Inhibition of succinate dehydrogenase sensitizes cyclin E-driven ovarian cancer to CDK inhibition

The Role of Succinic Acid Metabolism in Ovarian Cancer

Ovarian cancer is one of the most common malignancies and the highest mortality among gynecological malignancy. The standard therapy options for patients with ovarian cancer are cytoreductive surgery and chemotherapy, and although most patients do better with standard treatment, it is easy to relapse and be resistant to chemotherapy. Therefore, it is important to find new therapeutic strategies. More recently, metabolic reprogramming has been recognized as a hallmark of cancer and has become a potential target for tumor therapy. Mutations of metabolic enzymes are closely related to the development of ovarian cancer. The metabolic reprogramming of ovarian cancer not only provides energy to tumor cells, but also participates in various biological processes as signaling molecules. Succinic acid (SA) is an important metabolic intermediate involved in a number of metabolic pathways, such as TCA cycle and glutamine metabolism, and is also widely present in a variety of plants and vegetables. Studies show abnormal SA metabolism in many tumors and affect tumor formation through a variety of mechanisms. But the role of SA in ovarian cancer is less studied. This paper reviews the role of SA and its abnormal metabolic pathway in ovarian cancer.

Dual inhibition of FGFR4 and BCL-xL inhibits multi-resistant ovarian cancer with BCL2L1 gain

Aim: Overexpression of BCL2L1 (BCL-xL) was associated with platinum resistance in ovarian cancer (OvCa). However, role of copy number (CN) gain of BCL2L1 in OvCa remains elusive.

Methods: In silico analyses of multiple public datasets were perform. Validation was carried out in our tissue microarray (TMA) of OvCa cases. In vitro and in vivo assays was performed to explore potential targeted compound against BCL2L1-gained OvCa.

Results: BCL2L1 was gained in ~60% of OvCa. BCL2L1 was differentially expressed between healthy and cancerous ovarian cases. BCL2L1 gain was not prognostic either in overall or in progression-free survival but higher BCL2L1 expression was associated with worsened survival, indicating biological distinction between CN gain and overexpression of the gene. BCL2L1 gain was associated with multi-resistance to various drug with no significant sensitivity to any single agent. Only CRISPR-mediated BCL2L1 knockout, but not shRNA could be inhibitive. Combined genetic silencing of FGFR4/NCAM and BCL2L1 with shRNA induced potent inhibition of BCL2L1-gained OvCa with durable effect. Combined inhibition of FGFR/BCL-xL was required for inhibiting BCL2L1-gained OvCa in vitro and in vivo. Only dual inhibition of FGFR/BCL-xL without platinum was tolerable in vivo.

Conclusion: Gain of BCL2L1 is associated with resistance to multiple anti-cancer agents in OvCa. Dual inhibition of FGFR4 and BCL-xL showed potent effect and tolerable toxicity, holding promise to further translation.

GCN-5/PGC-1α signaling is activated and associated with metabolism in cyclin E1-driven ovarian cancer

AIM

We previously found Cyclin E1-driven high grade serous ovarian cancer (HGSOC) showed metabolic shift. In this study, we aimed to elucidate signaling pathway therein.

METHODS

In silico reproduction of TCGA ovarian cancer dataset and pathway analysis were performed. Candidate metabolic pathway was validated using in vitro and in vivo assays.

RESULTS

We found CCNE1-amplified HGSOC showed significant metabolic alteration besides canonical cell cycle control. Using CCNE1-amplified OVCAR-3 and A2780 OvCa cells, we found that knockdown of CDK2 and GCN5 resulted in decreased G6PC and increased PGC-1α level, and that both genetic and pharmaceutical (MB-3) inhibition of GCN5 resulted in significant decrease in acetylation of PGC-1α. Silencing of CDK2 also resulted in significant decrease in acetylation of both PGC-1α and Rb. GCN5-KD significantly decreased glucose uptake, increased lactate production and decreased SDH activity. Western blots showed hierarchy of the elements indicating Cyclin E1-CDK2/GCN5/PGC-1α regulatory axis from up- to down- stream. Inhibitory effect of Dinaciclib was similar to that of GCN5 silencing, whereas combination therapy further inhibited cell proliferation significantly. Similar findings were noted also in cell cycle arrest, apoptosis, invasion, migration and colony formation assays. Xenograft experiments showed that GCN5-KD alone did not alter tumor growth yet combination therapy of Dinaciclib and GCN5-KD conferred significant inhibition of tumor growth compared with either therapy alone with no toxicity observed.

CONCLUSION

GCN-5/PGC-1α signaling is activated and associated with metabolism in Cyclin E1-driven HGSOC. Targeting GCN5 hold promise to augment current CDK2-targeting strategy and further studies are warranted for clinical translation.