Cheng, L.-T. | bioRxiv Science

bioRxiv2025

MEX3A control of mitochondrial fitness is essential for ovarian clear cell carcinoma tumorigenesis and liver metastasis

Ovarian cancer (OC) is highly metastatic and chemoresistant. Due to heterogeneity among OC subtypes, the mechanisms underlying OC malignancy and metastasis remain largely unknown. Ovarian clear cell carcinoma (OCCC) accounts for 5-25% of OC and its incidence rate is rising. Liver metastasis is particularly high in OCCC patients and leads to significantly reduced median survival. Why OCCC metastasizes to liver at such high frequency remains elusive. We previously identified MEX3A as a key factor that promotes OCCC tumorigenesis in part by circumventing p53-mediated ferroptosis. Here, we report that MEX3A control of mitochondrial fitness, which occurs independently of p53, is essential for OCCC primary tumor growth and liver metastasis. MEX3A depletion resulted in chronic mitochondrial fragmentation and accumulation of non-functional mitochondria. MEX3A-depleted cells had decreased mitochondrial membrane potential, increased superoxide and decreased NAD+/NADH ratio, resulting in inhibition of oxidative phosphorylation (OXPHOS) and decreased ATP levels. In an environment enriched with mitophagy stressors, such as the liver, MEX3A-depleted OCCC cells had greatly reduced survival due to failure to recover from mitophagy. Consistent with these observations, MEX3A knockdown greatly reduced liver metastasis. Together, these data demonstrate that MEX3A-mediated mitochondrial fitness is a major factor underlying its p53-independent promotion of OCCC tumorigenesis and liver metastasis. Thus, targeting MEX3A will be a promising strategy to inhibit OCCC progression. Statement of significanceUnexpected effects of MEX3A on mitochondrial fitness indicate that the need for high MEX3A expression is an OCCC vulnerability that can be exploited to uncover new treatment strategies.

cancer biology↗

bioRxiv2025

BMAL2 is a druggable target for ARID1A-wildtype ovarian clear cell carcinoma (OCCC)

Ovarian clear cell carcinoma (OCCC) is highly chemo-resistant and has worse clinical outcome at advanced stages than other ovarian cancer subtypes. The most frequent ([~]50%) alterations in OCCC are AT-rich interactive domain 1A gene (ARID1A) mutations which lead to ARID1A deficiency. However, OCCC that retains ARID1A function differs substantially from ARID1A mutated OCCC. Particularly, targeted therapies that sensitize ARID1A-deficient OCCC to DNA damage are largely ineffective against OCCC with wild-type (wt) ARID1A. Thus, it is important to identify druggable targets and develop targeted therapies specifically for ARID1A-wt OCCC. We identified BMAL2 as a critical OCCC oncogene that promotes tumorigenesis by preventing DNA damage from endogenous origins. BMAL2 depletion altered expression of genes in DNA damage repair pathways, including RAD51, a core enzyme of the homologous recombination (HR) pathway. This led to double-stranded break accumulation, decreased cell viability and reduced tumor growth. This dependence on BMAL2 to maintain DNA integrity and cell viability can be a new route to suppress ARID1A-wt OCCC. Consistent with this idea, we found that GW833972A, a cannabinoid receptor agonist, bound BMAL2 with high affinity and facilitated its degradation. This in turn reduced RAD51 expression, leading to an accumulation of DNA damage and decreased cell viability. Xenograft models further demonstrated that GW833972A treatment alone inhibited ARID1A-wt OCCC tumor growth. Together, our findings reveal an essential oncogenic role of BMAL2 and demonstrate that it is an appealing therapeutic target, especially for ARID1A-wt OCCC. Statement of significanceBMAL2 depletion, or degradation by a small molecule, led to DNA damage accumulation, decreased cell viability and reduced tumorigenesis of ARID1A-wildtype ovarian clear cell carcinoma, indicating that BMAL2 is an appealing therapeutic target for treating this malignant disease.

cancer biology↗