Inhibition of phosphatidylinositol-3-kinase synergizes with gemcitabine in low-passage tumor cell lines correlating with Bax translocation to the mitochondria

Abstract

Apoptotic pathways, including the phosphatidylinositol-3-kinase (PI3K)/AKT survival pathway, are altered in most cancer cells in relation to their normal counterparts and these differences may present an excellent therapeutic window. To gain insight into the relevance of the PI3K pathway as a target for drug discovery we generated tumor cell lines from different tumor samples that we maintained at low passage. The characterization of these cell lines indicates that all of them have constitutively activated the PI3K pathway through different mechanisms. All cell lines were differentially sensitive to the PI3K inhibitor LY294002. Our data also support previous work indicating that PI3K inhibition might help classical chemotherapeutic treatments such as gemcitabine and strengthen suboptimal doses that might be effective for these purposes in decreasing the risk of side-effects. Finally, the analysis of the molecular markers that might be implicated in the synergism between LY294002 and gemcitabine suggests that PI3K inhibition might aid chemotherapeutic treatment, leading to changes in the balance between anti- and pro-apoptotic molecules of the Bcl-2 family, Bcl-XL and Bax. These results facilitate the exploration of potential synergism between chemotherapeutic treatment and the search for others that can account for similar molecular mechanisms of cooperation.

Inhibiting PI3K as a therapeutic strategy against cancer

“…LY294002 increases cytotoxicity induced by antimicrotubule agents such as taxanes and vinca alkaloids in glioma, ovarian cancer, oesophageal cancer, sarcoma and lung cancer cells in vitro and in vivo [100][101][102][103]. Wortmannin treatment sensitised cells to paclitaxel, cisplatin, gemcitabine or 5-fl uorouracil [100,104,105], where potentiation of apoptosis caused by wortmannin was associated with inhibition of AKT activation.…”

Targeting Melanoma with Dual Phosphoinositide 3-Kinase/Mammalian Target of Rapamycin Inhibitors

“…Here, a collection of human melanoma cell lines generated from different tumor stages and three mouse melanoma lines of the B16 family were used to investigate the susceptibility of melanoma to PI3K pathway inhibition. Currently, the effect of PI3K inhibition on cell proliferation is controversial (12,22,(24)(25)(26)(27); therefore, we first reevaluated the effect of the classic PI3K inhibitors wortmannin and LY294002. When cells were exposed to a single dose of inhibitor for 3 days, wortmannin was ineffective due to its limited stability ( Fig.…”

MutantPIK3CA-Bearing Colon Cancer Cells Display Increased Metastasis in an Orthotopic Model

“…The PI3K/AKT signaling pathway regulates several transcriptional factors, including the forkhead transcription factor FKHR and nuclear factor-nB, which are involved in cell cycle control and apoptosis (7)(8)(9)(10)(11). The PI3K/AKT pathway has also been reported to regulate multiple downstream signaling effectors relevant to apoptosis, including the Bcl-2 family member Bad, Bax, caspase-9, c-myc, and YAP (12,13). Furthermore, the PI3K/AKT pathway has been shown to inhibit apoptotic processes, although inhibition of PI3K/AKT signaling sensitizes cells to apoptotic stimuli, such as drug treatment or cellular stress (14,15).…”

“…Recent studies suggested that Bax promotes apoptosis through several interdependent mechanisms, including translocation of Bax from the cytoplasm to the mitochondria, Bax conformational changes, and oligomerization of Bax and Bak (13,(16)(17)(18). Bax expression is closely related to cellular sensitivity to apoptosis.…”