EP334/#194 Single cell transcriptomic analysis of a low grade serous ovarian cancer patient treated with pressurized intraperitoneal aerosolized chemotherapy (PIPAC)

Objectives

Low grade serous (LGS) ovarian cancer (OC) patients with recurrent peritoneal metastases (PM) have poor prognoses due to inherently chemo-resistant tumors. PIPAC is an intraperitoneal (IP) treatment that intensifies chemotherapy delivery to PM via drug nebulization and pressurization. We analyzed the molecular and tumor microenvironment (TME) changes of a PIPAC-treated LGS patient.

Methods

A heavily pretreated, recurrent LGS OC patient underwent PIPAC (aerosolized cisplatin 10.5 mg/m2 and doxorubicin 2.1 mg/m2, at 12 mmHg), via laparoscopy q6 weeks, for two cycles (NCT04329494). Tumor and normal peritoneum were biopsied immediately before and after each PIPAC. After cancer cell and nuclei isolation, sc-RNAseq was performed. 10X Genomics generated cDNA libraries were sequenced on Illumina HiSeq 2500 or NovaSeq 6000 instruments using 150 cycle paired-end sequencing at a depth of 10K reads/cell. Multiplex immunohistochemistry (IHC) was performed (quad staining PAX5-DAB/PD-L1/CD68/Tryptase; triple staining PD-1/CD8/CD3; double staining FOXP3-DAB/PD-1).

Results

The Peritoneal Carcinomatosis Index (PCI) reduced from 20 to 14 after one cycle. scRNAseq of post-PIPAC tumors demonstrated significantly upregulated immune and KRAS signaling pathways, compared to post-PIPAC normal tissues. Acute PIPAC-induced responses included upregulation of immune pathways (inflammatory response, complement, interferon-gamma response), hormonal signaling (androgen, estrogen late response), TNF-a signaling via NF-kB, apoptosis, and hypoxia pathways. PD-1 expression was increased in tumor infiltrating lymphocytes (TILs) within cancer islands.

Conclusions

PIPAC induces peritoneal tumor regression in LGS OC, possibly via modulation of TME, and upregulation of immune and KRAS signaling pathways; thus suggesting potential future combination with MEK inhibitors and immunotherapies.