Journal

Biochimica et Biophysica Acta (BBA) - General Subjects

Papers (4)

A dual PI3 kinase/mTOR inhibitor BEZ235 reverses doxorubicin resistance in ABCB1 overexpressing ovarian and pancreatic cancer cell lines

Multi-drug resistance (MDR) develops because cancer cells evade toxicity of several structurally unrelated drugs. Besides other mechanisms, MDR is linked to the overexpression of ATP Binding Cassette (ABC), transporters, among which ABCB1 is the best characterized one. Since overactivation of PI3K/Akt/mTOR plays a pivotal role in the growth of human cancers, we hypothesized whether dual PI3K and mTOR inhibitor, BEZ235 (BEZ, dactolisib) reverses resistance to doxorubicin (DOX). Ovarian (A2780) and pancreatic (MiaPaca2) cancer cells were used to generate DOX-resistant clones by overexpressing ABCB1 or stepwise treatment of DOX. Intracellular accumulation of DOX was measured by flow cytometry after treatment with BEZ. BEZ treatment caused an increase in intracellular levels of DOX which was almost identical to the naïve parental cell lines. BEZ was found to be a weak substrate for ABCB1 as demonstrated by minimal increase in ATPase activity. BEZ treatment caused a dose-dependent decrease in cell viability in combination with DOX, which was associated with an increase in cleaved PARP expression in the drug resistant clones. These results suggest that BEZ is a non-substrate inhibitor of ABCB1 and is able to effectively re-sensitize cells overexpressing ABCB1 to the effects of DOX. Dual PI3 Kinase/mTOR inhibitor, BEZ, has the potential to reverse MDR in cancer patients.

USP33-mediated stabilization of c-Myc drives glycolytic reprogramming and promotes ovarian cancer progression

Ovarian cancer (OC) is one of the most lethal gynecological malignancies, characterized by late-stage presentation, high recurrence rates, and a lack of effective early diagnostic markers. Recent evidence suggests that deubiquitinating enzymes (DUBs) play pivotal roles in tumor development and metabolic reprogramming. Here, we identify and characterize the function of the deubiquitinase USP33 in regulating c-Myc stability and glycolytic metabolism in OC. Through quantitative PCR (qPCR) and Western blot analyses, we show that USP33 is significantly upregulated in both OC tissues and cell lines compared to normal controls. Functional assays reveal that USP33 knockdown markedly inhibits cell proliferation, migration, and invasion while promoting apoptosis. Metabolically, USP33 silencing reduces glucose uptake, lactate production, and the extracellular acidification rate, consistent with downregulation of key glycolytic enzymes (LDHA, GLUT1, and PKM2). Mechanistically, co-immunoprecipitation and ubiquitination assays demonstrate that USP33 interacts with and deubiquitinates c-Myc at K48-linked chains, thereby stabilizing c-Myc protein levels and enhancing its transcriptional activity. Moreover, c-Myc overexpression rescues the inhibitory effects of USP33 knockdown on both glycolysis and malignant phenotypes. Clinically, high USP33 expression correlates with poor prognosis, suggesting that the USP33-c-Myc axis may serve as both a prognostic biomarker and a potential therapeutic target. Taken together, our findings highlight a critical role for USP33 in OC pathogenesis by mediating c-Myc-driven glycolytic reprogramming, and they provide new insights for developing targeted treatment strategies aimed at disrupting this pathway.

HERC4 modulates ovarian cancer cell proliferation by regulating SMO-elicited hedgehog signaling

HERC4 has been reported to have functions in several types of tumors, but its roles in ovarian cancer have not been studied yet. Primary tissues from ovarian cancer patients and cell lines were collected for real-time PCR. Kaplan-Meier Plotter was used to predict the prognosis of ovarian cancer patients. HERC4 was overexpressed in cells by lentivirus, and CCK-8 assay was performed to evaluate cell viability. Real-time PCR and Western blot were carried out to analyze the mRNA and protein expression, respectively. Xenograft tumor models were established to analyze HERC4 function in vivo. Firstly, we found that HERC4 was significantly downregulated in ovarian cancer. We then found that ovarian cancer patients with high HERC4 expression had significantly higher overall survival and progression-free survival rates compared with patients with low expression. Then, HERC4 was overexpressed in ovarian cancer cells, and we found that overexpression of HERC4 significantly inhibited ovarian cancer cell growth, as well as the expression of the target protein SMO, and the key proteins in the downstream hedgehog signaling pathway. Finally, the xenograft tumor models revealed that overexpression of HERC4 significantly inhibited tumor growth in vivo. Overall, these results indicate that overexpression of HERC4 inhibits cell proliferation of ovarian cancer in vitro and in vivo, suggesting that HERC4 may serve as an effective target for the treatment of ovarian cancer.

Publisher

Elsevier BV

ISSN

0304-4165

Biochimica et Biophysica Acta (BBA) - General Subjects