One-third of all estrogen receptor (ER)–positive breast tumors treated with endocrine therapy fai... more One-third of all estrogen receptor (ER)–positive breast tumors treated with endocrine therapy fail to respond, and the remainder is likely to relapse in the future. Almost all data on endocrine resistance has been obtained in models of invasive ductal carcinoma (IDC). However, invasive lobular carcinomas (ILC) comprise up to 15% of newly diagnosed invasive breast cancers each year and, whereas the incidence of IDC has remained relatively constant during the last 20 years, the prevalence of ILC continues to increase among postmenopausal women. We report a new model of Tamoxifen (TAM)-resistant invasive lobular breast carcinoma cells that provides novel insights into the molecular mechanisms of endocrine resistance. SUM44 cells express ER and are sensitive to the growth inhibitory effects of antiestrogens. Selection for resistance to 4-hydroxytamoxifen led to the development of the SUM44/LCCTam cell line, which exhibits decreased expression of ERα and increased expression of the estro...
Established human breast cancer cell lines are widely used as experimental models in breast cance... more Established human breast cancer cell lines are widely used as experimental models in breast cancer research. While these cell lines and their variants share many phenotypic characteristics with human breast tumors, the extent to which they reflect the underlying molecular biology of breast cancer remains controversial. We explored this issue using a probabilistic rather than heuristic approach. Data from gene expression microarrays were used to compare the global structures of the transcriptomes of three estrogen receptor alpha positive (ER +) human breast cancer cell lines (MCF-7, T47D, ZR-75-1) and 13 human breast tumors (11 ER + ; 2 ER-). Linear representations of the respective data structures were obtained by deriving those top principal components (PCs) required to capture ≥80% of the cumulative variance for each data set (M PCs). We then identified those genes most highly correlated with the M PCs (Pearson's correlation coefficient r≥0.800) and identified a group of 36 genes commonly correlated with both the cell line (M = 5 PCs) and tumor (M = 6 PCs) data structures. All 36 common genes were correlated with PC1 from the breast tumor data: 21/36 genes were correlated with PC1, 14/36 genes correlated with PC2, and 1/36 genes correlated with PC3 from the cell line data. Genes important in defining the data structures include NFκB p65, IGFBP-6, ornithine decarboxylase-1, and paxillin. When data from MDA-MB-435 xenografts (ER-) were included in the analysis, we were unable to find any common genes between these xenografts and the breast tumors. These data clearly imply that MCF-7, T47D, and ZR-75-1 cells and ER + breast tumors share substantial global similarities in the structures of their respective transcriptomes, and that these cell lines are good models in which to identify molecular events that are likely to be important in some ER + human breast cancers.
International Journal of Radiation Oncology*Biology*Physics
PURPOSE/OBJECTIVE(S) Following definitive treatment for localized prostate cancer a subset of men... more PURPOSE/OBJECTIVE(S) Following definitive treatment for localized prostate cancer a subset of men will unfortunately develop recurrent disease. Newer PET agents have demonstrated that most early recurrences occur in the abdominopelvic nodal basins. The optimal treatment strategy for this patient population is unknown but likely includes a combination of systemic therapy, surgery and/or radiation therapy. For radiation therapy, the optimal treatment volume, fractionation schedule and dose remain unanswered questions. We report early outcomes for patients treated with involved field SBRT for nodal oligo-recurrent prostate cancer. MATERIALS/METHODS Between January 2018 and January 2020, 21 patients with nodal oligo-recurrent prostate cancer treated with involved field SBRT at a single academic institution were eligible for inclusion in this analysis. Detection of recurrence was ascertained by imaging including: Axumin PET/CT (66%) or MRI/CT (34%) following a PSA rise. All patients were treated with five-fraction involved field SBRT to a dose of 27.5-30 Gy. The treatment volume for involved field was defined as the nodal basin containing the gross nodal disease as well as the immediately adjacent nodal basins. Oligo-recurrence was defined as any volume of disease that could be safely treated within an involved field. Acute and late toxicity data was defined as any treatment related toxicity occurring ≤ 90 days and > 90 days following treatment, respectively. Toxicity was graded using Common Terminology Criteria for Adverse Events version 4.0. PSA response was defined as any decrease in the PSA following treatment. Local recurrence was defined as any new or growing lesion within the treatment field following treatment. Local control was calculated using the Kaplan-Meier method. RESULTS The median pre-salvage PSA was 7.2 ng/ml. The median follow-up for all patients was 25 months (11 - 36 months). The most common acute side effect was grade 1 diarrhea (n = 7, 33%). Acute grade 2 GI toxicity occurred in 14% of patients (n = 3). Two patients had late low grade pelvic pain and 1 patient had late grade 2 lower extremity limb edema. There were no late grade 2+ GI side effects. No grade 3+ side effects occurred at any time following treatment. 88% of patients had a PSA response following treatment. The local control at 1 and 2 years was 100% and 94%, respectively. CONCLUSION With the widespread adoption of novel PET agents the group of patients with oligo-recurrent nodal disease is likely to increase significantly. The optimal combination of local and systemic therapy in this patient population is the subject of ongoing clinical investigation. With a favorable toxicity profile, high rates of local control and PSA response, involved field SBRT represents a feasible as well as convenient local therapy treatment option for an elderly patient population.
Unfolded protein response (UPR), a stress-induced survival mechanism, may be used by cancer cells... more Unfolded protein response (UPR), a stress-induced survival mechanism, may be used by cancer cells to avoid cell death. Antiestrogen therapy, widely applied in the treatment of estrogen receptor-positive (ER+) breast cancer, induces endoplasmic reticulum stress (EnR stress) that leads to activation of each of the three arms of the UPR. One critical prosurvival activator that is regulated by two arms of the UPR is the transcription factor X-box binding protein 1 (XBP1). XBP1 exists in two isoforms, the transcriptionally inactive unspliced XBP1(U) and the spliced, active XBP1(S). Overexpression of XBP1(S) confers estrogen independence and antiestrogen resistance in ER+ breast cancer cells and XBP1(S) expression correlates with poor clinical responsiveness to Tamoxifen in ER+ breast tumors. However, the underlying signaling mechanisms regulated by XBP1, which may mediate its effects on antiestrogen resistance, are unknown. We show that depletion of endogenous XBP-1 by siRNA increases apoptosis, decreases autophagy, requires down-regulation of p65/RelA, a component of the pro-survival NFκB complex. Using novel spliced and non-spliceable forms of XBP1, we show that XBP1(U) and XBP1(S) both regulate NFκB activity via ERα signaling in breast cancer cells. XBP1(S), but not XBP1(U), also can regulate p65/RelA expression independent of ERα. Antiestrogen resistance as conferred by XBP1 overexpression in MCF-7 cells requires the activation of NFκB signaling; inhibition of NFκB signaling by either the small molecule NFκB inhibitor Parthenolide or p65/RelA siRNA sensitizes XBP1 overexpressing cells to Tamoxifen. The activation of XBP1 and the downstream NFκB signaling is likely to contribute to the TMEM33 overepxression induced apoptosis, as both NFκB signaling and XBP1(S) are elevated in TMEM33 overexpressed MCF7 cells. Thus, we have identified a critical regulatory link between the UPR/XBP1 pathway and pro-survival NFκB signaling that is a major contributor to endocrine responsiveness in ER positive breast cancer. Citation Format: Clarke R, Hu R, Warri A, Jin L, Zwart A, Riggins R, Fang H-b. Both spliced and unspliced XBP1 regulates breast cancer cell fate response to antiestrogen via NFkappaB signaling [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-12.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2010
Resistance to endocrine therapies remains a major problem in the management of estrogen receptor-... more Resistance to endocrine therapies remains a major problem in the management of estrogen receptor-alpha (ER)-positive breast cancer. We show that inhibition of NF-kappaB (p65/RELA), either by overexpression of a mutant IkappaB (IkappaBSR) or a small-molecule inhibitor of NF-kappaB (parthenolide; IC(50)=500 nM in tamoxifen-resistant cells), synergistically restores sensitivity to 4-hydroxytamoxifen (4HT) in resistant MCF7/RR and MCF7/LCC9 cells and further sensitizes MCF-7 and MCF7/LCC1 control cells to 4HT. These effects are independent of changes in either cell cycle distribution or in the level of autophagy measured by inhibition of p62/SQSTM1 expression and cleavage of LC3. NF-kappaB inhibition restores the ability of 4HT to decrease BCL2 expression, increase mitochondrial membrane permeability, and induce a caspase-dependent apoptotic cell death in resistant cells. Each of these effects is reversed by a caspase 8 (CASP8)-specific inhibitor that blocks enzyme-substrate binding. Th...
Established human breast cancer cell lines are widely used as experimental models in breast cance... more Established human breast cancer cell lines are widely used as experimental models in breast cancer research. While these cell lines and their variants share many phenotypic characteristics with human breast tumors, the extent to which they reflect the underlying molecular biology of breast cancer remains controversial. We explored this issue using a probabilistic rather than heuristic approach. Data from gene expression microarrays were used to compare the global structures of the transcriptomes of three estrogen receptor alpha positive (ER + ) human breast cancer cell lines (MCF-7, T47D, ZR-75-1) and 13 human breast tumors (11 ER + ; 2 ER -). Linear representations of the respective data structures were obtained by deriving those top principal components (PCs) required to capture ≥80% of the cumulative variance for each data set (M PCs). We then identified those genes most highly correlated with the M PCs (Pearson's correlation coefficient r≥0.800) and identified a group of 36 genes commonly correlated with both the cell line (M = 5 PCs) and tumor (M = 6 PCs) data structures. All 36 common genes were correlated with PC1 from the breast tumor data: 21/36 genes were correlated with PC1, 14/36 genes correlated with PC2, and 1/36 genes correlated with PC3 from the cell line data. Genes important in defining the data structures include NFκB p65, IGFBP-6, ornithine decarboxylase-1, and paxillin. When data from MDA-MB-435 xenografts (ER -) were included in the analysis, we were unable to find any common genes between these xenografts and the breast tumors. These data clearly imply that MCF-7, T47D, and ZR-75-1 cells and ER + breast tumors share substantial global similarities in the structures of their respective transcriptomes, and that these cell lines are good models in which to identify molecular events that are likely to be important in some ER + human breast cancers.
Purpose: Estrogen receptor-a (ERa)-targeted therapies including tamoxifen (TAM) or Faslodex (ICI)... more Purpose: Estrogen receptor-a (ERa)-targeted therapies including tamoxifen (TAM) or Faslodex (ICI) are used to treat ER þ breast cancers. Up to 50% of tumors will acquire resistance to these interventions. Autophagy has been implicated as a major driver of antiestrogen resistance. We have explored the ability of hydroxychloroquine (HCQ), which inhibits autophagy, to affect antiestrogen responsiveness. Experimental Design: TAM-resistant MCF7-RR and ICI-resistant/TAM cross-resistant LCC9 ER þ breast cancer cells were injected into mammary fat pads of female athymic mice and treated with TAM and/or ICI in combination with oral low-dose HCQ. Results: We show that HCQ can increase antiestrogen responsiveness in MCF7-RR and LCC9 cells and tumors, likely through the inhibition of autophagy. However, the combination of ICIþHCQ was less effective than HCQ alone in vivo, unlike the TAMþHCQ combination. Antiestrogen treatment stimulated angiogenesis in tumors but did not prevent HCQ effectiveness. The lower efficacy of ICIþHCQ was associated with ICI effects on cell-mediated immunity within the tumor microenvironment. The mouse chemokine KC (CXCL1) and IFNg were differentially regulated by both TAM and ICI treatments, suggesting a possible effect on macrophage development/activity. Consistent with these observations, TAMþHCQ treatment increased tumor CD68 þ cells infiltration, whereas ICI and ICIþHCQ reduced peripheral tumor macrophage content. Moreover, macrophage elimination of breast cancer target cells in vitro was reduced following exposure to ICI. Conclusion: HCQ restores antiestrogen sensitivity to resistant tumors. Moreover, the beneficial combination of TAMþHCQ suggests a positive outcome for ongoing neoadjuvant clinical trials using this combination for the treatment of ER þ ductal carcinoma in situ lesions. Clin Cancer Res; 1-11. Ó2014 AACR. 42 tumors fail to respond (de novo resistance) or acquire 43 resistance over time (2-4). 44 Autophagy is a process by which a double membrane 45 vesicle surrounds cellular contents, such as damaged orga-46 nelles and misfolded or protein aggregates, and recycles 47 the material through lysosomal degradation (5). Studies in 48 breast cancer cells show that the induction of autophagy by 49 various therapeutics is usually prosurvival (6-8). Further-50 more, TAM and ICI both induce autophagy in ER þ breast 51 cancer cells (6, 9-13). Antiestrogen-resistant cell lines 52 exhibit increased basal autophagy when compared with 53 their antiestrogen-sensitive parental cells (10). Inhibiting 54 autophagy through autophagy-related gene 5 (ATG5) 55 silencing potentiated antiestrogen-mediated cell death, 56 indicating that antiestrogen-stimulated autophagy is pro-57 survival and a critical mechanism of therapy resistance (10). 58 Analysis of publically available human datasets indicates 59 that autophagy-related genes, ATG5, ATG7, and p62 60 (SQSTM1), are elevated in early recurring breast cancer 61 when compared with breast cancer that never recurs. More-62 over, elevated p62 is significantly correlated with poor 63 survival in patients with breast cancer (Supplementary Fig. 64 S1), suggesting a role for autophagy in breast cancer reoc-65 currence (14-18).
Biochimica et Biophysica Acta (BBA) - Reviews on Cancer, 2009
The use of endocrine agents is a safe and effective treatment in the management of hormone-sensit... more The use of endocrine agents is a safe and effective treatment in the management of hormone-sensitive breast cancer. Unfortunately, sooner or later, tumor cells develop resistance to endocrine manipulation making useless this approach. During the last decade, new molecules and intracellular signaling pathways involved in endocrine resistance have been identified. Several studies have documented that estrogen receptor signaling may maintain a pivotal role in the tumor growth despite the failure of a previous hormonal treatment. In this review we will discuss the general principles for optimizing the choice of endocrine therapy based on an understanding of the molecular mechanisms responsible for resistance to the different anti-hormonal agents.
One-third of all estrogen receptor (ER)–positive breast tumors treated with endocrine therapy fai... more One-third of all estrogen receptor (ER)–positive breast tumors treated with endocrine therapy fail to respond, and the remainder is likely to relapse in the future. Almost all data on endocrine resistance has been obtained in models of invasive ductal carcinoma (IDC). However, invasive lobular carcinomas (ILC) comprise up to 15% of newly diagnosed invasive breast cancers each year and, whereas the incidence of IDC has remained relatively constant during the last 20 years, the prevalence of ILC continues to increase among postmenopausal women. We report a new model of Tamoxifen (TAM)-resistant invasive lobular breast carcinoma cells that provides novel insights into the molecular mechanisms of endocrine resistance. SUM44 cells express ER and are sensitive to the growth inhibitory effects of antiestrogens. Selection for resistance to 4-hydroxytamoxifen led to the development of the SUM44/LCCTam cell line, which exhibits decreased expression of ERα and increased expression of the estro...
Established human breast cancer cell lines are widely used as experimental models in breast cance... more Established human breast cancer cell lines are widely used as experimental models in breast cancer research. While these cell lines and their variants share many phenotypic characteristics with human breast tumors, the extent to which they reflect the underlying molecular biology of breast cancer remains controversial. We explored this issue using a probabilistic rather than heuristic approach. Data from gene expression microarrays were used to compare the global structures of the transcriptomes of three estrogen receptor alpha positive (ER +) human breast cancer cell lines (MCF-7, T47D, ZR-75-1) and 13 human breast tumors (11 ER + ; 2 ER-). Linear representations of the respective data structures were obtained by deriving those top principal components (PCs) required to capture ≥80% of the cumulative variance for each data set (M PCs). We then identified those genes most highly correlated with the M PCs (Pearson's correlation coefficient r≥0.800) and identified a group of 36 genes commonly correlated with both the cell line (M = 5 PCs) and tumor (M = 6 PCs) data structures. All 36 common genes were correlated with PC1 from the breast tumor data: 21/36 genes were correlated with PC1, 14/36 genes correlated with PC2, and 1/36 genes correlated with PC3 from the cell line data. Genes important in defining the data structures include NFκB p65, IGFBP-6, ornithine decarboxylase-1, and paxillin. When data from MDA-MB-435 xenografts (ER-) were included in the analysis, we were unable to find any common genes between these xenografts and the breast tumors. These data clearly imply that MCF-7, T47D, and ZR-75-1 cells and ER + breast tumors share substantial global similarities in the structures of their respective transcriptomes, and that these cell lines are good models in which to identify molecular events that are likely to be important in some ER + human breast cancers.
International Journal of Radiation Oncology*Biology*Physics
PURPOSE/OBJECTIVE(S) Following definitive treatment for localized prostate cancer a subset of men... more PURPOSE/OBJECTIVE(S) Following definitive treatment for localized prostate cancer a subset of men will unfortunately develop recurrent disease. Newer PET agents have demonstrated that most early recurrences occur in the abdominopelvic nodal basins. The optimal treatment strategy for this patient population is unknown but likely includes a combination of systemic therapy, surgery and/or radiation therapy. For radiation therapy, the optimal treatment volume, fractionation schedule and dose remain unanswered questions. We report early outcomes for patients treated with involved field SBRT for nodal oligo-recurrent prostate cancer. MATERIALS/METHODS Between January 2018 and January 2020, 21 patients with nodal oligo-recurrent prostate cancer treated with involved field SBRT at a single academic institution were eligible for inclusion in this analysis. Detection of recurrence was ascertained by imaging including: Axumin PET/CT (66%) or MRI/CT (34%) following a PSA rise. All patients were treated with five-fraction involved field SBRT to a dose of 27.5-30 Gy. The treatment volume for involved field was defined as the nodal basin containing the gross nodal disease as well as the immediately adjacent nodal basins. Oligo-recurrence was defined as any volume of disease that could be safely treated within an involved field. Acute and late toxicity data was defined as any treatment related toxicity occurring ≤ 90 days and > 90 days following treatment, respectively. Toxicity was graded using Common Terminology Criteria for Adverse Events version 4.0. PSA response was defined as any decrease in the PSA following treatment. Local recurrence was defined as any new or growing lesion within the treatment field following treatment. Local control was calculated using the Kaplan-Meier method. RESULTS The median pre-salvage PSA was 7.2 ng/ml. The median follow-up for all patients was 25 months (11 - 36 months). The most common acute side effect was grade 1 diarrhea (n = 7, 33%). Acute grade 2 GI toxicity occurred in 14% of patients (n = 3). Two patients had late low grade pelvic pain and 1 patient had late grade 2 lower extremity limb edema. There were no late grade 2+ GI side effects. No grade 3+ side effects occurred at any time following treatment. 88% of patients had a PSA response following treatment. The local control at 1 and 2 years was 100% and 94%, respectively. CONCLUSION With the widespread adoption of novel PET agents the group of patients with oligo-recurrent nodal disease is likely to increase significantly. The optimal combination of local and systemic therapy in this patient population is the subject of ongoing clinical investigation. With a favorable toxicity profile, high rates of local control and PSA response, involved field SBRT represents a feasible as well as convenient local therapy treatment option for an elderly patient population.
Unfolded protein response (UPR), a stress-induced survival mechanism, may be used by cancer cells... more Unfolded protein response (UPR), a stress-induced survival mechanism, may be used by cancer cells to avoid cell death. Antiestrogen therapy, widely applied in the treatment of estrogen receptor-positive (ER+) breast cancer, induces endoplasmic reticulum stress (EnR stress) that leads to activation of each of the three arms of the UPR. One critical prosurvival activator that is regulated by two arms of the UPR is the transcription factor X-box binding protein 1 (XBP1). XBP1 exists in two isoforms, the transcriptionally inactive unspliced XBP1(U) and the spliced, active XBP1(S). Overexpression of XBP1(S) confers estrogen independence and antiestrogen resistance in ER+ breast cancer cells and XBP1(S) expression correlates with poor clinical responsiveness to Tamoxifen in ER+ breast tumors. However, the underlying signaling mechanisms regulated by XBP1, which may mediate its effects on antiestrogen resistance, are unknown. We show that depletion of endogenous XBP-1 by siRNA increases apoptosis, decreases autophagy, requires down-regulation of p65/RelA, a component of the pro-survival NFκB complex. Using novel spliced and non-spliceable forms of XBP1, we show that XBP1(U) and XBP1(S) both regulate NFκB activity via ERα signaling in breast cancer cells. XBP1(S), but not XBP1(U), also can regulate p65/RelA expression independent of ERα. Antiestrogen resistance as conferred by XBP1 overexpression in MCF-7 cells requires the activation of NFκB signaling; inhibition of NFκB signaling by either the small molecule NFκB inhibitor Parthenolide or p65/RelA siRNA sensitizes XBP1 overexpressing cells to Tamoxifen. The activation of XBP1 and the downstream NFκB signaling is likely to contribute to the TMEM33 overepxression induced apoptosis, as both NFκB signaling and XBP1(S) are elevated in TMEM33 overexpressed MCF7 cells. Thus, we have identified a critical regulatory link between the UPR/XBP1 pathway and pro-survival NFκB signaling that is a major contributor to endocrine responsiveness in ER positive breast cancer. Citation Format: Clarke R, Hu R, Warri A, Jin L, Zwart A, Riggins R, Fang H-b. Both spliced and unspliced XBP1 regulates breast cancer cell fate response to antiestrogen via NFkappaB signaling [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-12.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2010
Resistance to endocrine therapies remains a major problem in the management of estrogen receptor-... more Resistance to endocrine therapies remains a major problem in the management of estrogen receptor-alpha (ER)-positive breast cancer. We show that inhibition of NF-kappaB (p65/RELA), either by overexpression of a mutant IkappaB (IkappaBSR) or a small-molecule inhibitor of NF-kappaB (parthenolide; IC(50)=500 nM in tamoxifen-resistant cells), synergistically restores sensitivity to 4-hydroxytamoxifen (4HT) in resistant MCF7/RR and MCF7/LCC9 cells and further sensitizes MCF-7 and MCF7/LCC1 control cells to 4HT. These effects are independent of changes in either cell cycle distribution or in the level of autophagy measured by inhibition of p62/SQSTM1 expression and cleavage of LC3. NF-kappaB inhibition restores the ability of 4HT to decrease BCL2 expression, increase mitochondrial membrane permeability, and induce a caspase-dependent apoptotic cell death in resistant cells. Each of these effects is reversed by a caspase 8 (CASP8)-specific inhibitor that blocks enzyme-substrate binding. Th...
Established human breast cancer cell lines are widely used as experimental models in breast cance... more Established human breast cancer cell lines are widely used as experimental models in breast cancer research. While these cell lines and their variants share many phenotypic characteristics with human breast tumors, the extent to which they reflect the underlying molecular biology of breast cancer remains controversial. We explored this issue using a probabilistic rather than heuristic approach. Data from gene expression microarrays were used to compare the global structures of the transcriptomes of three estrogen receptor alpha positive (ER + ) human breast cancer cell lines (MCF-7, T47D, ZR-75-1) and 13 human breast tumors (11 ER + ; 2 ER -). Linear representations of the respective data structures were obtained by deriving those top principal components (PCs) required to capture ≥80% of the cumulative variance for each data set (M PCs). We then identified those genes most highly correlated with the M PCs (Pearson's correlation coefficient r≥0.800) and identified a group of 36 genes commonly correlated with both the cell line (M = 5 PCs) and tumor (M = 6 PCs) data structures. All 36 common genes were correlated with PC1 from the breast tumor data: 21/36 genes were correlated with PC1, 14/36 genes correlated with PC2, and 1/36 genes correlated with PC3 from the cell line data. Genes important in defining the data structures include NFκB p65, IGFBP-6, ornithine decarboxylase-1, and paxillin. When data from MDA-MB-435 xenografts (ER -) were included in the analysis, we were unable to find any common genes between these xenografts and the breast tumors. These data clearly imply that MCF-7, T47D, and ZR-75-1 cells and ER + breast tumors share substantial global similarities in the structures of their respective transcriptomes, and that these cell lines are good models in which to identify molecular events that are likely to be important in some ER + human breast cancers.
Purpose: Estrogen receptor-a (ERa)-targeted therapies including tamoxifen (TAM) or Faslodex (ICI)... more Purpose: Estrogen receptor-a (ERa)-targeted therapies including tamoxifen (TAM) or Faslodex (ICI) are used to treat ER þ breast cancers. Up to 50% of tumors will acquire resistance to these interventions. Autophagy has been implicated as a major driver of antiestrogen resistance. We have explored the ability of hydroxychloroquine (HCQ), which inhibits autophagy, to affect antiestrogen responsiveness. Experimental Design: TAM-resistant MCF7-RR and ICI-resistant/TAM cross-resistant LCC9 ER þ breast cancer cells were injected into mammary fat pads of female athymic mice and treated with TAM and/or ICI in combination with oral low-dose HCQ. Results: We show that HCQ can increase antiestrogen responsiveness in MCF7-RR and LCC9 cells and tumors, likely through the inhibition of autophagy. However, the combination of ICIþHCQ was less effective than HCQ alone in vivo, unlike the TAMþHCQ combination. Antiestrogen treatment stimulated angiogenesis in tumors but did not prevent HCQ effectiveness. The lower efficacy of ICIþHCQ was associated with ICI effects on cell-mediated immunity within the tumor microenvironment. The mouse chemokine KC (CXCL1) and IFNg were differentially regulated by both TAM and ICI treatments, suggesting a possible effect on macrophage development/activity. Consistent with these observations, TAMþHCQ treatment increased tumor CD68 þ cells infiltration, whereas ICI and ICIþHCQ reduced peripheral tumor macrophage content. Moreover, macrophage elimination of breast cancer target cells in vitro was reduced following exposure to ICI. Conclusion: HCQ restores antiestrogen sensitivity to resistant tumors. Moreover, the beneficial combination of TAMþHCQ suggests a positive outcome for ongoing neoadjuvant clinical trials using this combination for the treatment of ER þ ductal carcinoma in situ lesions. Clin Cancer Res; 1-11. Ó2014 AACR. 42 tumors fail to respond (de novo resistance) or acquire 43 resistance over time (2-4). 44 Autophagy is a process by which a double membrane 45 vesicle surrounds cellular contents, such as damaged orga-46 nelles and misfolded or protein aggregates, and recycles 47 the material through lysosomal degradation (5). Studies in 48 breast cancer cells show that the induction of autophagy by 49 various therapeutics is usually prosurvival (6-8). Further-50 more, TAM and ICI both induce autophagy in ER þ breast 51 cancer cells (6, 9-13). Antiestrogen-resistant cell lines 52 exhibit increased basal autophagy when compared with 53 their antiestrogen-sensitive parental cells (10). Inhibiting 54 autophagy through autophagy-related gene 5 (ATG5) 55 silencing potentiated antiestrogen-mediated cell death, 56 indicating that antiestrogen-stimulated autophagy is pro-57 survival and a critical mechanism of therapy resistance (10). 58 Analysis of publically available human datasets indicates 59 that autophagy-related genes, ATG5, ATG7, and p62 60 (SQSTM1), are elevated in early recurring breast cancer 61 when compared with breast cancer that never recurs. More-62 over, elevated p62 is significantly correlated with poor 63 survival in patients with breast cancer (Supplementary Fig. 64 S1), suggesting a role for autophagy in breast cancer reoc-65 currence (14-18).
Biochimica et Biophysica Acta (BBA) - Reviews on Cancer, 2009
The use of endocrine agents is a safe and effective treatment in the management of hormone-sensit... more The use of endocrine agents is a safe and effective treatment in the management of hormone-sensitive breast cancer. Unfortunately, sooner or later, tumor cells develop resistance to endocrine manipulation making useless this approach. During the last decade, new molecules and intracellular signaling pathways involved in endocrine resistance have been identified. Several studies have documented that estrogen receptor signaling may maintain a pivotal role in the tumor growth despite the failure of a previous hormonal treatment. In this review we will discuss the general principles for optimizing the choice of endocrine therapy based on an understanding of the molecular mechanisms responsible for resistance to the different anti-hormonal agents.
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Papers by A. Zwart