(5-(2-4-bis((3s)-3-methylmorpholin-4-yl)pyrido(2-3-d)pyrimidin-7-yl)-2-methoxyphenyl)methanol and Triple-Negative-Breast-Neoplasms

Triple-negative breast cancer (TNBC) shows a higher malignant and poorer clinical outcome compared with other breast cancer subtypes. Albeit that chemotherapy is the first choice for TNBC treatment, rapid emergence of chemoresistance and variability of chemotherapeutic responses in TNBC patients call for novel therapeutic strategies. Here, we reported evidences highlighting that combination of BH3 mimetics and mTOR inhibitors could be a promising therapeutic strategy to improve TNBC treatment. Our results showed that combination of the BH3 mimetic ABT263 and typical mTOR inhibitors, BEZ235 or AZD8055, leads to efficient apoptosis in vitro. Tumor regression was significantly improved by combination therapy compared with either drug alone in the xenograft model. Further mechanistic investigations revealed that mTOR inhibitors induced the suppression of MCL-1; concomitantly, the expression level of PUMA was significantly upregulated in a FOXO3a-dependent manner. The specific changes of MCL-1 and PUMA facilitated the release of the apoptotic regulators, such as BIM, BAX, and BAK, to induce the activation of mitochondrial apoptotic pathway, thereby sensitizing the ABT263 activity in TNBC. Therefore, our findings provided evidences that mTOR inhibitors can enhance antitumor efficacy of BH3 mimetics via downregulating MCL-1 and upregulating PUMA in TNBC; it could be a promising therapeutic strategy to treat TNBC.

Topics: Aniline Compounds; Animals; Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Drug Synergism; Female; Forkhead Box Protein O3; Humans; Imidazoles; Mice, Nude; Models, Biological; Morpholines; Myeloid Cell Leukemia Sequence 1 Protein; Protein Biosynthesis; Protein Kinase Inhibitors; Proto-Oncogene Proteins; Quinolines; Sulfonamides; TOR Serine-Threonine Kinases; Triple Negative Breast Neoplasms; Up-Regulation

MEK inhibition activates PI3K/AKT/mTOR pathway in triple negative breast cancer (TNBC) cell lines. Combination of PI3K inhibitor and MEK1/2 inhibitor is not appropriate for PI3K inhibitor insensitive TNBC cell lines. This study was designed to investigate the effects of dual treatments with mTOR1/2 inhibitor AZD8055 and MEK1/2 inhibitor PD0325901 in MDA-MB-435 cell line. MEK1/2 inhibition led to activation of AKT, which is the downstream signaling protein of PI3K pathway. The combination inhibited the phosphorylation of AKT and therefore abolished the feedback interaction of two pathways. Cell proliferation assay and DNA replication assay demonstrated that the dual treatments led to a significant synergistic inhibition of cell cycle progression and cell proliferation.

Topics: Benzamides; Cell Line, Tumor; Cell Proliferation; Diphenylamine; Humans; MAP Kinase Kinase 1; MAP Kinase Kinase 2; Morpholines; Phosphorylation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; TOR Serine-Threonine Kinases; Triple Negative Breast Neoplasms

The putative tumour suppressor and apoptosis-promoting gene, growth arrest-specific 5 (GAS5), encodes long ncRNA (lncRNA) and snoRNAs. Its expression is down-regulated in breast cancer, which adversely impacts patient prognosis. In this preclinical study, the consequences of decreased GAS5 expression for breast cancer cell survival following treatment with chemotherapeutic agents are addressed. In addition, functional responses of triple-negative breast cancer cells to GAS5 lncRNA are examined, and mTOR inhibition as a strategy to enhance cellular GAS5 levels is investigated. Breast cancer cell lines were transfected with either siRNA to GAS5 or with a plasmid encoding GAS5 lncRNA and the effects on breast cancer cell survival were determined. Cellular responses to mTOR inhibitors were evaluated by assaying culture growth and GAS5 transcript levels. GAS5 silencing attenuated cell responses to apoptotic stimuli, including classical chemotherapeutic agents; the extent of cell death was directly proportional to cellular GAS5 levels. Imatinib action in contrast, was independent of GAS5. GAS5 lncRNA promoted the apoptosis of triple-negative and oestrogen receptor-positive cells but only dual PI3K/mTOR inhibition was able to enhance GAS5 levels in all cell types. Reduced GAS5 expression attenuates apoptosis induction by classical chemotherapeutic agents in breast cancer cells, providing an explanation for the relationship between GAS5 expression and breast cancer patient prognosis. Clinically, this relationship may be circumvented by the use of GAS5-independent drugs such as imatinib, or by restoration of GAS5 expression. The latter may be achieved by the use of a dual PI3K/mTOR inhibitor, to improve apoptotic responses to conventional chemotherapies.

Topics: Apoptosis; Benzamides; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Female; Gene Expression Regulation, Neoplastic; Humans; Imatinib Mesylate; MCF-7 Cells; Morpholines; Piperazines; Pyrimidines; RNA, Long Noncoding; TOR Serine-Threonine Kinases; Triple Negative Breast Neoplasms