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Improving breast cancer sensitivity to paclitaxel by increasing aneuploidy.

ABSTRACT: Predictive biomarkers for tumor response to neoadjuvant chemotherapy are needed in breast cancer. This study investigates the predictive value of 280 genes encoding proteins that regulate microtubule assembly and function. By analyzing 3 independent multicenter randomized cohorts of breast cancer patients, we identified 17 genes that are differentially regulated in tumors achieving pathological complete response (pCR) to neoadjuvant chemotherapy. We focused on the MTUS1 gene, whose major product, ATIP3, is a microtubule-associated protein down-regulated in aggressive breast tumors. We show here that low levels of ATIP3 are associated with an increased pCR rate, pointing to ATIP3 as a predictive biomarker of breast tumor chemosensitivity. Using preclinical models of patient-derived xenografts and 3-dimensional models of breast cancer cell lines, we show that low ATIP3 levels sensitize tumors to the effects of taxanes but not DNA-damaging agents. ATIP3 silencing improves the proapoptotic effects of paclitaxel and induces mitotic abnormalities, including centrosome amplification and multipolar spindle formation, which results in chromosome missegregation leading to aneuploidy. As shown by time-lapse video microscopy, ATIP3 depletion exacerbates cytokinesis failure and mitotic death induced by low doses of paclitaxel. Our results favor a mechanism by which the combination of ATIP3 deficiency and paclitaxel treatment induces excessive aneuploidy, which in turn results in elevated cell death. Together, these studies highlight ATIP3 as an important regulator of mitotic integrity and a useful predictive biomarker for a population of chemoresistant breast cancer patients.

SUBMITTER: Rodrigues-Ferreira S

PROVIDER: S-EPMC6876190 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Improving breast cancer sensitivity to paclitaxel by increasing aneuploidy.

Rodrigues-Ferreira Sylvie S Nehlig Anne A Moindjie Hadia H Monchecourt Clarisse C Seiler Cynthia C Marangoni Elisabetta E Chateau-Joubert Sophie S Dujaric Marie-Eglantine ME Servant Nicolas N Asselain Bernard B de Cremoux Patricia P Lacroix-Triki Magali M Arnedos Monica M Pierga Jean-Yves JY André Fabrice F Nahmias Clara C

Proceedings of the National Academy of Sciences of the United States of America 20191104 47

Predictive biomarkers for tumor response to neoadjuvant chemotherapy are needed in breast cancer. This study investigates the predictive value of 280 genes encoding proteins that regulate microtubule assembly and function. By analyzing 3 independent multicenter randomized cohorts of breast cancer patients, we identified 17 genes that are differentially regulated in tumors achieving pathological complete response (pCR) to neoadjuvant chemotherapy. We focused on the <i>MTUS1</i> gene, whose major ...[more]

PMID: 31685623

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Project description:The forkhead transcription factor FOXK2 plays a critical role in suppressing tumorigenesis and mediating cytotoxic drug action in breast cancer. However, the mechanism by which the biological function of FOXK2 is regulated remains poorly understood. Here, we investigated the role of SUMOylation in modulating FOXK2-mediated drug sensitivity. We identified SUMOylation consensus motifs within the FOXK2 sequence and constructed two SUMOylation-defective double mutants by converting lysine 527 and 633 to arginines and glutamic acid 529 and 635 to alanines, respectively. We found that both the FOXK2 SUMOylation-deficient (K527/633 R) and (E529/635 A) mutants were ineffective in mediating the cytotoxic function of paclitaxel when compared to the wild-type (WT) FOXK2. When overexpressed, unlike the wild-type (WT) FOXK2, the K527/633 R mutant had little effect on the sensitivity of MCF-7 and MDA-MB-231 cells to paclitaxel, as examined by cell viability and clonogenic assays. Our results also showed that MCF-7 cells overexpressing the K527/633 R mutant form of FOXK2 or the empty expression vector have lower protein and mRNA levels of its tumour suppressive transcriptional target FOXO3 compared to the wild-type FOXK2. Consistently, ChIP assays revealed that unlike wild-type FOXK2, the SUMOylation-defective (K527/633 R) mutant is unable to bind to the FOXO3 promoter, despite expressing comparable levels of protein and having the same subcellular localization as the wild-type FOXK2 in MCF-7 cells. Interestingly, expression of neither the wild-type nor the K527/633 R mutant FOXK2 had any effect on the proliferation and paclitaxel sensitivity of the MCF-7 TaxR paclitaxel-resistant cells. In agreement, both the wild-type and the (K527/633 R) mutant FOXK2 failed to bind to the endogenous FOXO3 promoter in these cells. Collectively, our results suggest that SUMOylation positively regulates FOXK2 transcriptional activity and has a role in mediating the cytotoxic response to paclitaxel through the tumour suppressor FOXO3.

Project description:The forkhead transcription factor FOXK2 has recently been implicated in cancer cell proliferation and survival, but a role in cancer chemotherapeutic drug resistance has hitherto not been explored. Here we demonstrate that FOXK2 has a central role in mediating the cytotoxic drug response in breast cancer. Clonogenic and cell viability assays showed that enhanced FOXK2 expression sensitizes MCF-7 breast cancer cells to paclitaxel or epirubicin treatment, whereas FOXK2 depletion by small interfering RNAs (siRNAs) confers drug resistance. Our data also showed that the activation of the tumour suppressor FOXO3a by paclitaxel and epirubicin is mediated through the induction of FOXK2, as depletion of FOXK2 by siRNA limits the induction of FOXO3a by these drugs in MCF-7 cells. Chromatin immunoprecipitation (ChIP) analysis showed that in response to drug treatment, FOXK2 accumulates and binds to the proximal FOXO3a promoter region in MCF-7 cells. Furthermore, we also uncovered that FOXK2 is deregulated and, therefore, can express at high levels in the nucleus of both the paclitaxel and epirubicin drug-resistant MCF-7 cells. Our results showed that ectopically overexpressed FOXK2 accumulates in the nuclei of drug-resistant MCF-7 cells but failed to be recruited to target genes, including FOXO3a. Crucially, we found that FOXO3a is required for the anti-proliferative and epirubicin-induced cytotoxic function of FOXK2 in MCF-7 cells by sulphorhodamine and clonogenic assays. The physiological importance of the regulation of FOXO3a by FOXK2 is further confirmed by the significant correlations between FOXO3a and FOXK2 expression in breast carcinoma patient samples. Further survival analysis also reveals that high nuclear FOXK2 expression significantly associates with poorer clinical outcome, particularly in patients who have received conventional chemotherapy, consistent with our finding that FOXK2 is deregulated in drug-resistant cells. In summary, our results suggest that paclitaxel and epirubicin target the FOXK2 to modulate their cytotoxicity and deregulated FOXK2 confers drug resistance.

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Improving breast cancer sensitivity to paclitaxel by increasing aneuploidy.

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Improving breast cancer sensitivity to paclitaxel by increasing aneuploidy.

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