Hypoxia Promotes Synergy between Mitomycin C and Bortezomib through a Coordinated Process of Bcl-xL Phosphorylation and Mitochondrial Translocation of p53

Abstract

Colorectal peritoneal carcinomatosis (CPC) exhibits severe tumor hypoxia, leading to drug resistance and disease aggressiveness. This study demonstrates that the combination of the chemotherapeutic agent mitomycin C with the proteasome inhibitor bortezomib induced synergistic cytotoxicity and apoptosis, which was even more effective under hypoxia in colorectal cancer cells. The combination of mitomycin C and bortezomib at sub-lethal doses induced activation of c-Jun NH2-terminal kinase and p38 mitogen-activated protein kinase and resulted in Bcl-xL phosphorylation at Serine 62, leading to dissociation of Bcl-xL from pro-apoptotic Bak. Interestingly, the intracellular level of p53 became elevated and p53 translocated to the mitochondria during the combinatorial treatment, in particular under hypoxia. The coordinated action of Bcl-xL phosphorylation and p53 translocation to the mitochondria resulted in conformational activation of Bak oligomerization, facilitating cytochrome c release and apoptosis induction. In addition, the combinatorial treatment with mitomycin C and bortezomib significantly inhibited intraperitoneal tumor growth in LS174T cells and increased apoptosis, especially under hypoxic conditions in vivo. This study provides a preclinical rationale for the use of combination therapies for CPC patients. Implications The combination of a chemotherapy agent and proteasome inhibitor at sub-lethal doses induced synergistic apoptosis, in particular under hypoxia, in vitro and in vivo through coordinated action of Bcl-xL and p53 on Bak activation.

Tepary Bean (Phaseolus acutifolius) Lectins Induce Apoptosis and Cell Arrest in G0/G1 by P53(Ser46) Phosphorylation in Colon Cancer Cells

“…In this sense, when p53 is phosphorylated in serine 46, it induces signaling pathways triggering apoptosis by stopping the cell cycle [37,43,44]. Our results suggest that p53 mutations in HT-29 cells do not affect the phosphorylation in ser46 and TBLF treatment increases the p-p53(ser46) level at 8 h. Similar results have been observed in various studies for lectin-mediated cell death induction pathways [27,[45][46][47][48].…”

Novel Anthraquinone Compounds Inhibit Colon Cancer Cell Proliferation via the Reactive Oxygen Species/JNK Pathway

“…The reduction in Bcl-2/Bax ratio was determined as a marker of an apoptosis signaling [48]. Numerous studies have shown that phosphorylation of Bcl-xL(S62), but not Bcl-2, induces cell apoptosis via Bax oligomerization in the mitochondria and cytochrome c release in the cytoplasm [22,49]. However, the results showed that both Bcl-2 and Bcl-xL were phosphorylated after treatment with 8a, therefore, the specific mechanism of 8a-induced HCT116 cell apoptosis needs further study.…”

Enhancement of human bladder carcinoma cell chemosensitivity to Mitomycin C through quasi-monochromatic blue light (λ = 453 ± 10 nm)

“…Mitomycin C (MMC; medac GmbH; Wedel, Germany), an alkylating chemotherapy which binds covalently to the DNA, leads to cross-linking and therefor inhibits the replication of the DNA 28 was obtained from the local university pharmacy at a concentration of 1 mg/ml. Due to data of preliminary works [29][30][31] and our own experiments we used MMC in a concentration of 10 µg/ml for all further experiments.…”