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BET inhibition increases βIII-tubulin expression and sensitizes metastatic breast cancer in the brain to vinorelbine.

ABSTRACT: Metastases from primary breast cancer result in poor survival. βIII-tubulin (TUBB3) has been established as a therapeutic target for breast cancer metastases specifically to the brain. In this study, we conducted a systematic analysis to determine the regulation of TUBB3 expression in breast cancer metastases to the brain and strategically target these metastases using vinorelbine (VRB), a drug approved by the U.S. Food and Drug Administration (FDA). We found that human epidermal growth factor receptor 2 (HER2) signaling regulates TUBB3 expression in both trastuzumab-sensitive and trastuzumab-resistant neoplastic cells. We further discovered that bromodomain and extra-terminal domain (BET) inhibition increases TUBB3 expression, rendering neoplastic cells more susceptible to apoptosis by VRB. Orthotopic xenograft assays using two different breast cancer cell models revealed a reduction in tumor volume with BET inhibition and VRB treatment. In addition, in vivo studies using a model of multiple brain metastasis (BM) showed improved survival with the combination of radiation + BET inhibitor (iBET-762) + VRB (75% long-term survivors, P < 0.05). Using in silico analysis and BET inhibition, we found that the transcription factor myeloid zinc finger-1 (MZF-1) protein binds to the TUBB3 promoter. BET inhibition decreases MZF-1 expression and subsequently increases TUBB3 expression. Overexpression of MZF-1 decreases TUBB3 expression and reduces BM in vivo, whereas its knockdown increases TUBB3 expression in breast cancer cells. In summary, this study demonstrates a regulatory mechanism of TUBB3 and provides support for an application of BET inhibition to sensitize breast cancer metastases to VRB-mediated therapy.

SUBMITTER: Kanojia D

PROVIDER: S-EPMC8276250 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:IntroductionPyrotinib plus capecitabine has been approved in China for human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). Meanwhile, vinorelbine is another important chemotherapy option for MBC available in oral and intravenous forms. Thus, pyrotinib plus vinorelbine may represent a new treatment option, particularly for patients with failed capecitabine treatment. This study reported the first real-world data for pyrotinib plus vinorelbine therapy in HER2+ MBC.MethodsHER2+ MBC patients (n = 97) treated with pyrotinib plus vinorelbine in six institutions across China from May 2018 to June 2020 were enrolled. Progression-free survival (PFS), objective response rate (ORR), overall survival (OS), and toxicity profiles were determined.ResultsSixty-seven percent of patients received more than two lines of systematic therapy. Nearly all patients (97.9%) had received trastuzumab and 50.5% were administered lapatinib. When combined with pyrotinib, 74.2% received oral and 25.8% received intravenous vinorelbine. Median PFS (mPFS) was 7.8 (range, 4.7-10.8) months for all patients. The mPFS in patients administered pyrotinib as second-line therapy and third-or-higher-line therapy were 12.0 and 6.4 months, respectively. Patients who received pyrotinib plus oral or intravenous vinorelbine had similar mPFS (7.8 vs. 6.4 months, p = 0.871). The 23 patients with brain metastases had mPFS of 6.3 (range, 3.4-9.2) months. Lapatinib-naïve patients had significantly longer PFS than lapatinib-treated patients (10.8 months vs. 5.6 months, p = 0.020). Median OS was not achieved. The ORR for 96 patients was 34.3%. Common grade 3 and 4 adverse events were diarrhea (22.7%), neutropenia (7.2%), and leukopenia (4.1%).ConclusionsPyrotinib plus vinorelbine therapy demonstrated promising effects in HER2+ MBC with tolerable toxicity, particularly in patients with second-line treatment and without prior lapatinib treatment, as well as in patients with brain metastases. Oral vinorelbine is a useful alternative to the intravenous form when combined with pyrotinib.Clinical trial registration[ClinicalTrials.gov], identifier [NCT04517305].

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BET inhibition increases βIII-tubulin expression and sensitizes metastatic breast cancer in the brain to vinorelbine.

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