Project description:Estrogen receptor positive (ER+) breast cancers that develop resistance to therapies that target the ER are the most common cause of breast cancer death. Beyond mutations in ER, which occur in 25-30% of patients treated with aromatase inhibitors (AIs), our understanding of clinical mechanisms of resistance to ER-directed therapies remains incomplete. We identified activating HER2 mutations in metastatic biopsies from eight patients with ER+ metastatic breast cancer who had developed resistance to ER-directed agents, including AIs, tamoxifen, and fulvestrant. Examination of treatment-naïve primary tumors in five patients revealed no evidence of pre-existing mutations in four of five patients, suggesting that these mutations were acquired under the selective pressure of ER-directed therapy. These mutations were mutually exclusive with ER mutations, suggesting a distinct mechanism of acquired resistance to ER-directed therapies. In vitro analysis confirmed that these mutations conferred estrogen independence. In addition, and in contrast to ER mutations, these mutations resulted in resistance to tamoxifen, fulvestrant, and the CDK4/6 inhibitor palbociclib. Resistance was overcome by combining ER-directed therapy with the irreversible HER2 kinase inhibitor neratinib, highlighting an effective treatment strategy in these patients.
Project description:Beyond acquired mutations in the estrogen receptor (ER), mechanisms of resistance to ER-directed therapies in ER+ breast cancer have not been clearly defined. We conducted a genome-scale functional screen spanning 10,135 genes to investigate genes whose overexpression confer resistance to selective estrogen receptor degraders. Pathway analysis of candidate resistance genes demonstrated that the FGFR, ERBB, insulin receptor, and MAPK pathways represented key modalities of resistance. In parallel, we performed whole exome sequencing in paired pre-treatment and post-resistance biopsies from 60 patients with ER+ metastatic breast cancer who had developed resistance to ER-targeted therapy. The FGFR pathway was altered via FGFR1, FGFR2, or FGF3/FGF4 amplifications or FGFR2 mutations in 24 (40%) of the post-resistance biopsies. In 12 of the 24 post-resistance tumors exhibiting FGFR/FGF alterations, these alterations were not detected in the corresponding pre-treatment tumors, suggesting that they were acquired or enriched under the selective pressure of ER-directed therapy. In vitro experiments in ER+ breast cancer cells confirmed that FGFR/FGF alterations led to fulvestrant resistance as well as cross-resistance to the CDK4/6 inhibitor palbociclib, through activation of the MAPK pathway. The resistance phenotypes were reversed by FGFR inhibitors and, to a lesser extent, MEK inhibitors, suggesting potential treatment strategies.
Project description:Although the estrogen receptor (ER) positive variant of breast cancer is touted as the most indolent and favorable, the majority of breast cancer deaths are in fact from this subtype. There are several features of this category of breast cancers that likely account for this outcome. The first is that metastatic relapse can occur many years after initial diagnosis of primary disease. The second is that once the cancer cells awaken into full-blown metastatic disease, they are largely resistant to ER-directed therapies (i.e. hormonal therapy, HT). The third is that when metastases do occur, they are invariably in many locations. This observation suggests that these dormant/sleeping metastatic cells are “globally” awakened as if by a “systemic” infection. We suggest that these three processes be not only linked, but underlie the lethal features of metastatic disease. We hypothesized that mtDNA is necessary for the escape from therapy induced tumor dormancy of luminal breast cancer cells
Project description:Patients with estrogen-receptor-positive (ER+) breast cancer, the most common subtype, remain at risk for lethal metastatic disease years after diagnosis. Recurrence arises partly because tumor cells in bone marrow become resistant to estrogen-targeted therapy. Here, we utilized a co-culture model of bone marrow mesenchymal stem cells (MSCs) and ER+ breast cancer cells to recapitulate interactions of cancer cells in bone marrow niches. ER+ breast cancer cells in direct contact with MSCs acquire cancer stem-like (CSC) phenotypes with increased resistance to standard antiestrogenic drugs. We confirmed that co-culture with MSCs increased labile iron in breast cancer cells, a phenotype associated with CSCs and disease progression. Clinically approved iron chelators and in-house lysosomal iron-targeting compounds restored sensitivity to antiestrogenic therapy. These findings establish iron modulation as a mechanism to reverse MSC-induced drug resistance and suggest iron modulation in combination with estrogen-targeted therapy as a promising, translatable strategy to treat ER+ breast cancer.
Project description:Up to 40% of patients with Estrogen Receptor positive (ER+) breast cancer experience relapse. Breast cancer stem cells (BCSCs) are known to be involved in therapy resistance, relapse, and development of more aggressive and metastatic tumors. Therefore, there is an urgent need to identify genes/pathways that drive stem-like cell properties in ER+ breast tumors. Using single-cell RNA sequencing and bioinformatic approaches, with additional follow-up studies, we identified a unique quiescent stem-like cell population that is driven by ER and NFkB in multiple ER+ breast cancer models. Moreover, a gene signature derived from this stem-like population is expressed in endocrine therapy-resistant and metastatic cell populations and predictive of poor patient outcome. These findings indicate a novel role for ER and NFkB crosstalk in BCSCs biology and understanding the mechanism by which these pathways promote stem properties may be exploited to improve outcomes for ER+ breast cancer patients at risk of relapse.
Project description:HT induces an OXPHOS metabolic editing of ER+ breast cancers, paradoxically establishing HT-driven self-renewal of dormant CD133hi/ERlo cells mediating metastatic progression, which is sensitive to dual targeted therapy In this study, we demonstrated that CD133hi cells can mediate HT resistance and metastatic progression. Using human luminal breast cancer cell lines we have developed an in vivo model of spontaneous metastatic disease recapitulating what is observed in patients. Combining in vivo and in vitro studies we identified a de-novo cancer stem cell population (CSCs) “CD133hi/ERlo/Notch3hi/IL6hi”, which are generated from non-CSCs via the sustained suppression of ER activity. We provide evidence that an ER-IL6-IL6R-CD133 loop is a mechanism mediating HT-resistance.
Project description:Combined CDK4/6 inhibitor (CDK4/6i) and endocrine therapy significantly improves the outcome of patients with advanced estrogen receptor-positive (ER+) breast cancer. However, resistance to this treatment and resultant disease progression remains a major clinical challenge. High expression of the receptor tyrosine kinase REarranged during Transfection (RET) has been associated with resistance to endocrine therapy in breast cancer, but the role of RET in CDK4/6i treatment response/resistance remains unexplored. To identify gene expression alterations associated with resistance to combined endocrine therapy and CDK4/6i, we performed global gene expression analysis and RNA sequencing of two ER+ breast cancer cell models resistant to this combined therapy.