Combination Treatment Of Tamoxifen Research Articles

Cholesteryl ester transfer protein knock-down in conjunction with a cholesterol-depleting agent decreases tamoxifen resistance in breast cancer cells.

The cholesterogenic phenotype, encompassing de novo biosynthesis and accumulation of cholesterol, aids cancer cell proliferation and survival. Previously, the role of cholesteryl ester (CE) transfer protein (CETP) has been implicated in breast cancer aggressiveness, but the molecular basis of this observation is not clearly understood, which this study aims to elucidate. CETP knock-down resulted in a >50% decrease in cell proliferation in both 'estrogen receptor-positive' (ER+; Michigan Cancer Foundation-7 (MCF7) breast cancer cells) and 'triple-negative' breast cancer (TNBC; MDA-MB-231) cell lines. Intriguingly, the abrogation of CETP together with the combination treatment of tamoxifen (5 μM) and acetyl plumbagin (a cholesterol-depleting agent) (5 μM) resulted in twofold to threefold increase in apoptosis in both cell lines. CETP knockdown also showed decreased intracellular CE levels, lipid raft and lipid droplets in both cell lines. In addition, RT2 Profiler PCR array (Qiagen, Germany)-based gene expression analysis revealed an overall downregulation of genes associated in cholesterol biosynthesis, lipid signalling and drug resistance in MCF7 cells post-CETP knock-down. On the contrary, resistance in MDA-MB-231 cells was reduced through increased expression in cholesterol efflux genes and the expression of targetable surface receptors by endocrine therapy. The pilot xenograft mice study substantiated CETP's role as a cancer survival gene as knock-down of CETP stunted the growth of TNBC tumour by 86%. The principal findings of this study potentiate CETP as a driver in breast cancer growth and aggressiveness and thus targeting CETP could limit drug resistance via the reduction in cholesterol accumulation in breast cancer cells, thereby reducing cancer aggressiveness.

Abstract PO3-18-07: Therapeutic Potential of Combining Eltanexor with Tamoxifen to Treat Primary and Metastatic Estrogen Receptor Positive (ER+) Breast Cancers

Abstract Estrogen receptors are key pathway initiators in the aggressive development of more than two-thirds of all breast cancers. Tamoxifen (TAM) is a selective estrogen receptor modulator that disables the ER pathway and inhibits the progression of ER+ breast cancer. Unfortunately, 10-40% of patients with ER+ breast cancer who were treated with TAM experience recurrence and metastasis within 10 years. We have previously identified exportin 1 (XPO1) to be more highly expressed in breast cancers with acquired TAM resistance compared to TAM-sensitive counterparts and showed that a combination treatment of TAM with an XPO1 inhibitor, selinexor, is an effective method of tumor suppression in preclinical models. In this study we investigated the activity of eltanexor, an investigational second generation XPO1 inhibitor with minimal penetration of the blood-brain barrier, to inhibit cancer growth without leading to weight loss. Our results show that mice harboring MCF7-ESR1Y537Sxenograft tumors had significantly less (P < .05) flank tumor growth when administered a treatment regimen of TAM and eltanexor compared to control mice. In metastatic tumor models, we observed decreased metastatic burden in mice harboring MCF7-ESR1 D538G and MCF7-ESR1Y537S tumors when co-administered TAM and eltanexor. We did not observe weight changes in either model. Our findings suggest that eltanexor may be a relevant treatment for further exploration in the context of a TAM combination therapy for treatment of ER+ breast cancer. Citation Format: Vedant Jain, Myra Kamdar, Hannah McGee, Qianying Zuo, Jin Young Yoo, Yosef Landesman, Christopher Walker, Zeynep Madak-Erdogan. Therapeutic Potential of Combining Eltanexor with Tamoxifen to Treat Primary and Metastatic Estrogen Receptor Positive (ER+) Breast Cancers [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-18-07.

60P - Sensitization of estrogen receptor-positive breast cancer cells to tamoxifen by novel epi-oligomycin A

BackgroundBreast cancer is the most common cancer in women. Most breast tumors are ER(+)/hormone-dependent, this makes it possible to treat them with tamoxifen and other SERM/SERD drugs. Combination treatment of tamoxifen with novel drugs provides an efficient way for reduction of the drug concentration. The aim of the work was to obtain novel less toxic oligomycin derivatives for combinatorial treatment with tamoxifen. MethodsOligomycin A was produced at BIOAN (Moscow, Russia) using Streptomyces avermitilis NIC B62. The oligomycin derivatives were synthesized from oligomycin A. MCF-7 breast cancer cell line and MCF-10A human mammary epithelial cell line were obtained from the ATCC collection. Hormone-resistant subline was developed by long-term treatment of MCF-7line with tamoxifen. Antiproliferative activity was measured by MTT. ResultsA series of less toxic oligomycin A derivatives, selectively modified at the C-33 position of the side chain, was synthesized, and their activity against hormone-dependent breast cancer cells was tested. Lead compound, a (33S)-diastereomer of oligomycin A (epi-oligomycin A), was chosen, which showed high activity towards MCF-7 breast cancer cells and MCF-7/TR hormone-resistant cells. Low doses of tamoxifen and epi-oligomycin A, which had no significant effects on the growth of MCF-7 cells, were evaluated. In combination, low doses of tamoxifen and epi-oligomycin A caused a significant antiproliferative effects on MCF-7 cells. Moreover, it was possible to return the sensitivity of hormone-resistant subline to tamoxifen by epi-oligomycin A treatment. Non-malignant epithelial cells, MCF-10A, were less sensitive to epi-oligomycin A. ConclusionsNovel epi-oligomycin A enhances response to tamoxifen, which allows for reduction of the effective drug concentration. Combinatorial strategy with epi-oligomycin A may hold promise in development of therapies against breast tumours, including those with acquired resistance to the hormonal treatment. The research is supported by Russian Science Foundation (chemistry, agreement 15-15-00141) and the Russian Foundation for Basic Research (biology, 18-015-00422). Legal entity responsible for the studyThe authors. FundingRussian Science Foundation (chemistry, agreement 15-15-00141) and the Russian Foundation for Basic Research (biology, 18-015-00422). DisclosureAll authors have declared no conflicts of interest.

Downregulation of BAG‑1 in T47D cells promotes resistance to tamoxifen via activation of the PI3K/Akt/mTOR signaling pathway.

Tamoxifen, a selective estrogen receptor (ER) modulator, is the most widely used endocrine therapy for patients with ER‑positive breast cancer. However, ~30% of tamoxifen‑treated breast cancers do not initially respond to tamoxifen, and neither do they eventually develop tamoxifen resistance. Bcl‑2‑associated athanogene1 (BAG‑1) is a multifunctional protein that interacts with a wide range of molecules to protect cells from apoptosis otherwise induced by cytotoxic drugs, growth factor withdrawal, radiation and stress. The aim of the present study was to investigate the function of BAG‑1 in tamoxifen resistance. Immunohistochemistry techniques were used to determine BAG‑1 expression in 119 stageI‑III primary breast cancer tissues and it was identified that BAG‑1 was significantly overexpressed in ER‑positive breast cancer (P=0.001). Knockdown of BAG‑1 by short interfering RNA was revealed to downregulate ER, and upregulate phospho (p)‑protein kinaseB (Akt) and p‑mammalian target of rapamycin (mTOR) levels. Furthermore, significantly decreased tamoxifen‑induced apoptosis (41.70±1.93 vs. 55.03±2.39%; P=0.012) was observed in T47D cells following the silencing of BAG‑1. In contrast, overexpression of BAG‑1 long enhanced apoptosis (65.10±2.35 vs. 55.03±2.39%; P=0.039) in T47D cells treated with tamoxifen. Combination treatment of tamoxifen and an mTOR inhibitor restored the inhibitory effects of tamoxifen in T47D cells exhibiting low BAG‑1 expression levels (66.87±2.27 vs. 57.07±2.46%; P=0.037). In conclusion, there results of the present study indicated that suppression of BAG‑1 expression may activate the phosphoinositide3‑kinase/Akt/mTOR pathway and protect ER‑positive breast cancer cells from tamoxifen‑induced inhibition of proliferation. ER‑positive breast cancer cells exhibiting low BAG‑1 expression appeared to be more sensitive to treatment with the mTOR inhibitor rapamycin. Furthermore, the results indicated that combination treatment targeting ER with tamoxifen and targeting mTOR with rapamycin may significantly potentiate the inhibitory effect in BAG‑1‑silenced cells.

Agoraphobia and Follicle-Stimulating Hormone Levels between Tamoxifen and Goserelin versus Tamoxifen Alone in Premenopausal Hormone Receptor-Positive Breast Cancer: A 12-Month Prospective Randomized Study.

ObjectiveTamoxifen is an estrogen receptor antagonist used to prevent recurrence of breast cancer, which may provoke depression and anxiety and increase follicle-stimulating hormone (FSH) to patients. We compared anxiety and depression symptoms and FSH levels who received conventional tamoxifen alone and combination treatment of goserelin, a gonadotropin-releasing hormone (GnRH) analogue, with tamoxifen.MethodsSixty-four premenopausal women with hormone receptor-positive early-stage breast cancer were included and were assigned randomly to receive either tamoxifen and goserelin combination or tamoxifen alone for 12 months. The participants were evaluated blindly using the Hamilton Depression and Anxiety Rating Scale, the Beck Depression Rating Scale, and the Albany Panic and Phobia Questionnaire (APPQ). Blood FSH levels were assessed at baseline, 6 and 12 months.ResultsA significant time×group difference was detected in the agoraphobia trends subscale of the APPQ and in FSH levels. The combination group showed significantly less increases in agoraphobia subscale of APPQ and greater decreases in FSH level than those in the tamoxifen-alone group from baseline to 12 months of treatment. No significant differences for age, tumor grade, body mass index, or family history were found at baseline between the two groups.ConclusionOur results suggest that the combination treatment of tamoxifen and goserelin resulted in less agoraphobia than tamoxifen alone in premenopausal women with breast cancer, which may associated with FSH suppression of goserelin.

The potential in breast tissue engineering for the combined effects of linoleic acid and tamoxifen

Literature to date has strongly suggested that linoleic acid (LA) enhances mammary cancer cell proliferation when used in the range of 0·5–20 μg/ml. In contrast, the current in vitro studies show that deoxyribonucleic acid (DNA) levels of estrogen receptor-positive (ER+) MCF7 breast cancer cells were diminished following treatment with 30 μg/ml (100 μM) LA. MCF7 cells, when treated for 6 days with LA, consumed significantly less glucose than untreated controls (P-value<0·01). MFC7 cells treated with 30 μg/ml LA and 10 μM tamoxifen had even lower levels of DNA and lower glucose uptake. The same combination treatment of tamoxifen and LA was applied to a noncancerous mammary cell line, MCF10A, and did not have a significant effect on MCF10A DNA concentrations. Linoleic acid and its byproducts are important to cell proliferation and tissue reconstruction and, in combination with tamoxifen, can provide a uniquely different approach to soft tissue engineering. That is, LA and tamoxifen-loaded scaffolds may provide a viable reconstructive approach for patients undergoing lumpectomy and mastectomy by encouraging natural breast healing while limiting the ability of ER+ cancer cells to regrow. This approach could allow the suppression of estrogen-dependent mammary carcinomas while allowing natural cell proliferation after a mastectomy or lumpectomy.

Abstract P1-12-14: Retinoic acid sensitizes triple-negative breast cancer cells to tamoxifen treatment

Abstract Tamoxifen, an estrogen receptor (ER) antagonist, is often used as an adjuvant endocrine therapy in the successful treatment of ER+ breast tumors. Tumors that lack ER, progesterone receptor (PR) and HER2 expression (i.e. triple-negative breast cancers) cannot be treated with adjuvant endocrine therapies, like tamoxifen, and are often more aggressive. Inducing ER expression is a potential strategy for sensitization of triple-negative breast cancers to adjuvant endocrine therapies. Given recent evidence suggesting cross-talk between the retinoic acid (RA) and estrogen signaling pathways, we investigated if RA induces expression of ER in triple-negative breast cancer cells. We hypothesize that this would lead to sensitization of the cells to tamoxifen treatment. Quantitative PCR of mRNA isolated from triple-negative MDA-MB-231 cells treated with RA and estradiol had increased ER transcript levels. Furthermore, treatment with estradiol and RA synergistically induced increased expression of RA-inducible genes. In cell proliferation studies, neither RA nor estradiol treatment alone significantly altered the growth of MDA-MB-231 cells; however, when treated with both estradiol and RA together, the growth of the cells increased significantly. This suggests that the RA-mediated increase in ER expression sensitizes MDA-MB-231 cells to estradiol-induced cell growth. Next, we investigated whether the increased ER expression sensitized MDA-MB-231 cells to tamoxifen treatment. Tamoxifen did not decrease the growth of MDA-MB-231 cells; however, when applied in combination with both estradiol and RA, tamoxifen significantly reduced MDA-MB-231 proliferation. Furthermore, tamoxifen treatment reduced the synergistic effects of estradiol/RA on RA-inducible gene expression. Together, these results suggest that the use of RA in combination with tamoxifen warrants further investigation as a potential treatment for triple-negative breast cancers. The success of the combination treatment of tamoxifen and RA in the reduction of triple-negative breast cancer cell tumor xenografts will provide further justification for this strategy in the treatment of triple-negative breast cancers. Citation Format: Krysta M Coyle, Cheryl A Dean, Diana B Jo, Margaret Thomas, Mohammad Sultan, Paola Marcato. Retinoic acid sensitizes triple-negative breast cancer cells to tamoxifen treatment [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-12-14.

Abstract 2955: Effect of the combined treatment of TRA-8, an agonistic DR5 antibody, and tamoxifen on breast cancer cells.

Abstract Breast cancer affects an estimated 1.3 million women worldwide annually (Breast Cancer Res Tr 127(2): 541-7, 2011). Certain breast cancer cell types are resistant or become resistant to conventional chemotherapy (Cancer Sci 94: 15-21, 2003). The use of targeted therapy for the controlled killing of cancer cells has become clinically desirable to sensitize breast cancer to anti-cancer drugs. TRA-8, a death receptor 5 (DR5) agonistic antibody, has been shown to be effective in activating apoptosis in breast cancer cells (Molecular Cancer Res 9(4): 403-17, 2011). However, sensitivity to TRA-8 induced apoptosis is dependent on the breast cancer subtype (Clin Cancer Res 9: 3731-41, 2003). Tamoxifen (TMX) is known for its potency in the treatment of estrogen receptor (ER)-positive breast cancers, but some ER-positive breast cancers have developed resistance to TMX treatment (J. Natl. Cancer Inst, 96(12):926-35, 2004). TMX is an inhibitor of the ER-mediated cell growth pathway and TMX is also a calmodulin (CaM) antagonist. The goal of this study is to understand the effect of the combined treatment of TRA-8 and TMX on breast cancer cell apoptosis. We hypothesize that the combination treatment of TMX and TRA-8 will sensitize the ER-positive breast cancer cells to apoptosis. The ER-positive breast cancer cell lines: MCF-7 and T47D were treated with and without estradiol, and then treated with TRA-8 only, TMX only and combined TRA-8 and TMX. Results showed that both MCF-7 and T47D cells showed synergism between TMX and TRA-8 for the cells treated with estradiol, but showed antagonism for the cells without estradiol treatment. Co-immunoprecipitation experiments using a DR5 antibody demonstrated the interactions of CaM with DR5 in MCF-7 and T47D cell lines. The results suggested that TMX inhibited the estradiol activated ER cell growth pathway and the cross-talk between DR5-mediated apoptosis pathway and ER-mediated cell growth pathway contributed to the observed synergism between TMX and TRA-8 treatment for ER activated MCF-7 and T47D cells. The observed antagonism between TMX and TRA-8 treatment for ER inactivated MCF-7 and T47D cells could have resulted from TMX serving as a CaM antagonist to inhibit CaM-DR5 interactions and thus inhibit DR5-induced apoptosis. Results from this study provide the basis for further investigations of the role of CaM/DR5 binding in mediating breast cancer apoptosis and the cross-talk between DR5-mediated apoptosis and ER-mediated cell growth pathways, which may lead to the novel therapeutic strategies for breast cancer. Citation Format: Tiara Napier, Romone Fancy, Tong Zhou, John Mountz, Yuhua Song. Effect of the combined treatment of TRA-8, an agonistic DR5 antibody, and tamoxifen on breast cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2955. doi:10.1158/1538-7445.AM2013-2955

Genistein sensitizes inhibitory effect of tamoxifen on the growth of estrogen receptor‐positive and HER2‐overexpressing human breast cancer cells

Although tamoxifen (TAM) is used for the front-line treatment and prevention of estrogen receptor-positive (ER+) breast tumors, nearly 40% of estrogen-dependent breast tumors do not respond to TAM treatment. Moreover, the positive response is usually of short duration, and most tumors eventually develop TAM-resistance. Overexpression of HER2 gene is associated with TAM-resistance of breast tumor, and suppression of HER2 expression enhances the TAM activity. Soy isoflavone genistein has been shown to have anti-cancer activities and suppress expression of HER2 and ERalpha. The objective of this study was to test the hypothesis that genistein may sensitize the response of ER+ and HER2-overexpressing breast cancer cells to TAM treatment. The combination treatment of TAM and genistein inhibited the growth of ER+/HER2-overexpressing BT-474 human breast cancer cells in a synergistic manner in vitro. Determination of cellular markers indicated that this synergistic inhibitory effect might be contributed in part from combined effects on cell-cycle arrest at G(1) phase and on induction of apoptosis. Further determination of the molecular markers showed that TAM and genistein combination synergistically induced BT-474 cell apoptosis in part by synergistic downregulation of the expression of survivin, one of the apoptotic effectors, and downregulation of EGFR, HER2, and ERalpha expression. Our research may provide a novel approach for the prevention and/or treatment of TAM insensitive/resistant human breast cancer, and warrants further in vivo studies to verify the efficacy of genistein and TAM combination on the growth of ER+/HER2-overexpressing breast tumors and to elucidate the in vivo mechanisms of synergistic actions.