Chaoyun Pan

A noncanonical role of SAT1 enables anchorage independence and peritoneal metastasis in ovarian cancer

Anchorage-independent survival of ovarian tumor cells in ascites is the initial and critical step for peritoneal metastasis. How ovarian tumor cells achieve anchorage independence remains unclear. Here we show that a noncanonical role of spermidine/spermine N1-acetyltransferase 1 (SAT1) dictates anchorage-independent cell survival and potentiates metastatic dissemination in ovarian cancer. SAT1-high cancer cells are prevalent in ascitic tumors, and high SAT1 expression in primary tumors is linked to increased peritoneal metastasis rates in ovarian cancer patients. Mechanistically, SAT1 noncanonically acetylates H3K27 domains in multiple mitosis-regulating genes, increasing their transcriptional levels and protecting disseminating cells from aberrant mitosis and mitotic cell death. Notably, the acetylation of H3K27 by SAT1 depends on the reductive carboxylation of glutamine to supply acetyl-CoA in the nucleus. SAT1 inhibition with the small-molecule inhibitor ginkgolide B attenuates the metastatic tumor burden in mouse models. We conclude that SAT1 inhibition is a promising therapeutic strategy for metastatic ovarian cancer.

Serotonin-licensed macrophages potentiate chemoresistance via inositol metabolic crosstalk in ovarian cancer

Therapeutic resistance in solid tumors frequently stems from enhanced homologous recombination (HR) repair capacity, yet systemic regulators of this pathway remain poorly defined. Here, we identify a serotonin-sensitive tumor-associated macrophage (TAM) subpopulation that orchestrates inositol metabolic crosstalk to potentiate HR repair in cancer cells. This TAM subset exhibited marked enrichment in ovarian tumors with low response to chemotherapy. Mechanistically, peripheral serotonin activates these TAMs via serotonin receptor HTR7, triggering extracellular vesicle (EV) secretion enriched with inositol metabolic enzymes PI4K2A and ITPKC. EV-mediated transfer of these metabolic enzymes elevates nuclear inositol-1,3,4,5-tetraphosphate (IP4) in cancer cells, where IP4 directly binds MRE11 and facilitates MRE11-DNA binding and HR repair. Attenuating peripheral serotonin using fluoxetine-a selective serotonin reuptake inhibitor (SSRI) antidepressant-ablates TAM-derived EV delivering of inositol metabolic enzymes and sensitizes tumors to cisplatin/PARP inhibitor (PARPi). Our study unveils a systemic serotonin-primed metabolic crosstalk within the tumor microenvironment that potentiates chemoresistance, revealing targetable HR repair regulation beyond cancer-cell-autonomous mechanisms.

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.