GSK3β;NFATc1 subtype defines resistance in PDAC

Introduction Current studies demonstrate the existence of various molecularly and genetically defined subtypes of pancreatic cancer, but their clinical relevance and therapeutic potential are still largely unknown. An exception are tumors with gBRCA1/2 mutations, which are characterized by insufficient DNA repair and are candidates for platinum-based therapy and PARP inhibitors.

Aims The identification and characterization of novel subtypes with addressable vulnerabilities are at the center of our ongoing investigations.

Methods Established models of pancreatic carcinogenesis, murine and human PDAC cell lines, patient-derived-cell lines (CDX) and -organoids (PDO) were used for subtype identification and characterization experiments. RNA-seq, Western-blot, qPCR, flow-cytometry, immunohistochemistry, immunofluorescence, live-cell imaging, DNA damage repair assay, BrdU and MTT studies were carried out to characterize molecular, biochemical and functional features of the novel and clinical highly relevant GSK3β;NFATc1^high subtype.

Results Our studies revealed existence of a novel subtype in 15-20% of all PDAC samples that is defined by high levels of the GSK3β-NFATc1 transcription pathway. Moreover, GSK3β;NFATc1^high subtype correlates with disease progression, resistance and poor survival. We also showed that pharmacological or genetic inactivation of the GSK3β-NFATc1 pathway overcomes resistance in CDX and PDO through impaired homologous recombination (HR) and DNA repair. RNA-seq analyses identified GSK3β-NFATc1 regulated gene signatures involved in DNA repair, replication stress and HR, specifically BRCA1, BRCA2, Rad51. Immunofluorescence analysis confirmed NFATc1 dependent DNA repair in resistant PDAC cells, while HR repair assays showed a highly significant loss of HR activity upon disruption of the GSK3β-NFATc1 pathway. Finally, cisplatin induced resistance causes increased expression and activation of the GSK3β-NFATc1 pathway, whereas genetic silencing of NFATc1 not only increased basal and platin-induced DNA damage responses but also prevented PDAC subtype cells from recovery.

Conclusion The GSK3;NFATc1^high subtype defines a highly aggressive and resistant subgroup in pancreatic cancer. Moreover, targeted inactivation of the GSK3β-NFATc1 pathway causes an “inducible BRCAness” phenotype, thus resensitizing PDAC tumors to platin-based therapy.

Publication History

Article published online:
28 August 2023