The Role of JAK2/STAT3 Pathway in Ovarian Cancer Revealed by Single-Cell RNA Sequencing and Functional Assays

Introduction-

Each year, about 240,000 women worldwide are diagnosed with ovarian cancer. Ovarian cancer is treated with surgery and chemotherapy, but unfortunately patients will relapse even after an initial response. Development of resistance to chemotherapy and associated development of malignant abdominal fluid (ascites) is a major challenge for patients with advanced ovarian cancer. Inter- and intra-tumor heterogeneity of ovarian cancer cells and associated non-cancer cells are important factor driving treatment resistance, but remains poorly understood.

Materials and methods-

Single-cell RNA-sequencing (scRNA-seq) is a powerful tool for characterizing cancer and non-cancer cells. We performed scRNA-seq on cells isolated from abdominal ascites of 11 patients and patient-derivedmouse xenograft (PDX) during therapy and following relapse. Fresh specimens were immediately dissociated and thousands of single cells were sequenced and analyzed. This revealed 20 distinct cell clusters. Functional assays were used to measure tumor growth in PDX models and evaluate cellular drug sensitivity in 3D ex-vivo patient-derived cell cultures.

Results and discussion-

We applied scRNA-seq to >17,000 ascites cells isolated from 11 patients and revealed significant inter-individual variability in the cellular composition of ascites and the immunomodulatory functions of non-malignant cells. We found that previously described “immunoreactive” and “mesenchymal” expression subtypes of ovarian cancer cells are rather reflective of infiltration with immune cells and cancer-associated fibroblasts, respectively. Importantly, we uncovered a common feature of resistance to be the cancer cell-autonomous expression of inflammatory pathways, including the JAK/STAT-pathway. We treated PDX models with carboplatin, and profiled single-cells pre-treatment, at the time of minimal residual disease (MRD) and at relapse, and found expression of JAK/STAT pathway components to be expressed in MRD/relapse. JAK/STAT-inhibition efficiently eliminates cancer cells in ex vivo cultures derived from platinum-resistant patients, inhibits metastatic potential and invasion, prevents formation of malignant ascites, and leads to tumor regression in ovarian cancer PDX models.

This study elucidates novel and interesting features of the malignant ascites environment: asignificantinter-individualheterogeneityofnon-malignantcells, a precise description of non-tumor cell types that were previously described as cancer cells, and the indication that an intraperitoneal-injected JAK2/STAT3 inhibitor has local and systemic activity against ovarian cancer.

Conclusion-

We used a combined approach of scRNA-seq and functional assays to study the ecosystem of platinum-resistant ovarian cancer ascites using patients and PDX models, found a major regulator of this malignancy and provided a potential novel therapeutic strategy for ovarian cancer.