Tyrosine catabolism enhances genotoxic chemotherapy by suppressing translesion DNA synthesis in epithelial ovarian cancer.

Amino acid metabolism has been actively investigated as a potential target for antitumor therapy, but how it may alter the response to genotoxic chemotherapy remains largely unknown. Here, we report that the depletion of fumarylacetoacetate hydrolase (FAH), an enzyme that catalyzes the final step of tyrosine catabolism, reduced chemosensitivity in epithelial ovarian cancer (EOC). The expression level of FAH correlated significantly with chemotherapy efficacy in patients with EOC. Mechanistically, under genotoxic chemotherapy, FAH is oxidized at Met308 and translocates to the nucleus, where FAH-mediated tyrosine catabolism predominantly supplies fumarate. FAH-produced fumarate binds directly to REV1, resulting in the suppression of translesion DNA synthesis (TLS) and improved chemosensitivity. Furthermore, in vivo tyrosine supplementation improves sensitivity to genotoxic chemotherapeutics and reduces the occurrence of therapy resistance. Our findings reveal a unique role for tyrosine-derived fumarate in the regulation of TLS and may be exploited to improve genotoxic chemotherapy through dietary tyrosine supplementation.

ODF2L acts as a synthetic lethal partner with WEE1 inhibition in epithelial ovarian cancer models.

WEE1 has emerged as an attractive target in epithelial ovarian cancer (EOC), but how EOC cells may alter their sensitivity to WEE1 inhibition remains unclear. Here, through a cell cycle machinery-related gene RNAi screen, we found that targeting outer dense fiber of sperm tails 2-like (ODF2L) was a synthetic lethal partner with WEE1 kinase inhibition in EOC cells. Knockdown of ODF2L robustly sensitized cells to treatment with the WEE1 inhibitor AZD1775 in EOC cell lines in vitro as well as in xenografts in vivo. Mechanistically, the increased sensitivity to WEE1 inhibition upon ODF2L loss was accompanied by accumulated DNA damage. ODF2L licensed the recruitment of PKMYT1, a functionally redundant kinase of WEE1, to the CDK1-cyclin B complex and thus restricted the activity of CDK1 when WEE1 was inhibited. Clinically, upregulation of ODF2L correlated with CDK1 activity, DNA damage levels, and sensitivity to WEE1 inhibition in patient-derived EOC cells. Moreover, ODF2L levels predicted the response to WEE1 inhibition in an EOC patient-derived xenograft model. Combination treatment with tumor-targeted lipid nanoparticles that packaged ODF2L siRNA and AZD1775 led to the synergistic attenuation of tumor growth in the ID8 ovarian cancer syngeneic mouse model. These data suggest that WEE1 inhibition is a promising precision therapeutic strategy for EOC cells expressing low levels of ODF2L.

Platinum-Resistant Ovarian Cancer Is Vulnerable to the cJUN-XRCC4 Pathway Inhibition.

DNA double-strand breaks (DSBs) caused by platinum drugs are dangerous lesions that kill cancer cells in chemotherapy. Repair of DSB by homologous recombination (HR) and nonhomologous end joining (NHEJ) is frequently associated with platinum resistance in ovarian cancer. While the role of the HR pathway and HR-targeting strategy in platinum resistance is well studied, dissecting and targeting NHEJ machinery to overcome platinum resistance in ovarian cancer remain largely unexplored. Here, through an NHEJ pathway-focused gene RNAi screen, we found that the knockdown of XRCC4 significantly sensitized cisplatin treatment in the platinum-resistant ovarian cancer cell lines. Moreover, upregulation of XRCC4 is observed in a panel of platinum-resistant cell lines relative to the parental cell lines, as well as in ovarian cancer patients with poor progression-free survival. Mechanistically, the increased sensitivity to cisplatin upon XRCC4 knockdown was caused by accumulated DNA damage. In cisplatin-resistant ovarian cancer, the JNK-cJUN complex, activated by cisplatin, translocated into the nucleus and promoted the transcription of XRCC4 to confer cisplatin resistance. Knockdown of XRCC4 or treatment of the JNK inhibitor led to the attenuation of cisplatin-resistant tumor growth in the xenograft mouse models. These data suggest targeting XRCC4 is a potential strategy for ovarian cisplatin resistance in ovarian cancer.

ROS-regulated phosphorylation of ITPKB by CAMK2G drives cisplatin resistance in ovarian cancer.

Platinum resistance accounts for much of the high mortality and morbidity associated with ovarian cancer. Identification of targets with significant clinical translational potential remains an unmet challenge. Through a high-throughput synthetical lethal screening for clinically relevant targets using 290 kinase inhibitors, we identify calcium/calmodulin-dependent protein kinase II gamma (CAMK2G) as a critical vulnerability in cisplatin-resistant ovarian cancer cells. Pharmacologic inhibition of CAMK2G significantly sensitizes ovarian cancer cells to cisplatin treatment in vitro and in vivo. Mechanistically, CAMK2G directly senses ROS, both basal and cisplatin-induced, to control the phosphorylation of ITPKB at serine 174, which directly regulates ITPKB activity to modulate cisplatin-induced ROS stress. Thereby, CAMK2G facilitates the adaptive redox homeostasis upon cisplatin treatment and drives cisplatin resistance. Clinically, upregulation of CAMK2G activity and ITPKB pS174 correlates with cisplatin resistance in human ovarian cancers. This study reveals a key kinase network consisting of CAMK2G and ITPKB for ROS sense and scavenging in ovarian cancer cells to maintain redox homeostasis, offering a potential strategy for cisplatin resistance treatment.