The effect of chemotherapy on immune cells in the tumour microenvironment of high-grade serous ovarian cancer

The aim of this thesis was to understand the immune modulatory effects of chemotherapy in high-grade serous ovarian cancer (HGSOC). Using single cell RNA sequencing (scRNAseq) I studied the immune landscape of HGSOC omental metastasis from seven patients (three prechemotherapy and four postchemotherapy) with analysis of 64,097 cells in total. I also conducted scRNAseq on 69,781 cells from a HGSOC mouse model that is characterised clinically by marginal response to chemotherapy and transcriptionally by high TGF. The model replicated most of the human immune cell subpopulations. Chemotherapy enhanced host anti-tumour immune response pathways in human and mouse immune cells but this effect was counterbalanced by other immune-inhibitory effects in the same cell populations. I hypothesised that these inhibitory pathways could be targeted to improve response to chemotherapy. I found significant upregulation of the macrophage scavenger receptor Stabilin-1 postchemotherapy in human and mouse tumours. Blocking Stabilin-1 in vitro resulted in significant increase in TNF secretion by macrophages. Combining an anti-stabilin1 antibody with chemotherapy in the HGSOC mouse model led to a significant increase in overall survival compared to chemotherapy alone. Furthermore, it had some efficacy as a monotherapy. Response to the anti-stabilin1 plus chemotherapy combination was associated with the formation of lymphoid aggregates and a significant increase in CD8 T cell infiltrate. I also identified two immunosuppressive effects of chemotherapy on T cells: upregulation of FOXP3 and the TGF pathway. After some in vitro validation, I combined a FOXP3 or TGFR inhibitor with chemotherapy in the model. This also led to a significant increase in median survival over chemotherapy alone but neither of these inhibitors were effective as monotherapies. Overall, my results provide preliminary evidence for using novel immunotherapies to induce a more durable response to chemotherapy and prolong survival with a rationale for simultaneously targeting both macrophages and T cells

Sertoli-Leydig Cell Tumour and DICER1 Mutation: A Case Report and Review of the Literature

Sertoli-Leydig cell tumours of the ovary (SLCT) are rare tumours predominantly caused by mutations in the DICER1 gene. We present a patient with a unilateral SLCT who had an underlying germline DICER1 gene mutation. We discuss the underlying pathology, risks, and screening opportunities available to those with a mutation in this gene as SLCT is only one of a multitude of other tumours encompassing DICER1 syndrome. The condition is inherited in an autosomal dominant fashion. As such, genetic counselling is a key component of the management of women with SLCT

Semi-Supervised Analysis of Myeloid and T Cell Behaviour in ex vivo Ovarian Tumour Slices Reveals Changes in Cell Motility After Treatments

Source info: ISCIENCE-D-22-05047Source info: ISCIENCE-D-22-0504

Chemotherapy Induces Tumor-Associated Macrophages that Aid Adaptive Immune Responses in Ovarian Cancer

Neoadjuvant chemotherapy (NACT) may stimulate anticancer adaptive immune responses in high-grade serous ovarian cancer (HGSOC), but little is known about effects on innate immunity. Using omental biopsies from HGSOC, and omental tumors from orthotopic mouse HGSOC models that replicate the human tumor microenvironment, we studied the impact of platinum-based NACT on tumor-associated macrophages (TAM). We found that chemotherapy reduces markers associated with alternative macrophage activation while increasing expression of proinflammatory pathways, with evidence of inflammasome activation. Further evidence of a shift in TAM functions came from macrophage depletion via CSF1R inhibitors (CSF1Ri) in the mouse models. Although macrophage depletion in established disease had no impact on tumor weight or survival, CSF1Ri treatment after chemotherapy significantly decreased disease-free and overall survival. This decrease in survival was accompanied by significant inhibition of adaptive immune response pathways in the tumors. We conclude that chemotherapy skews the TAM population in HSGOC toward an antitumor phenotype that may aid adaptive immune responses, and therapies that enhance or sustain this during remission may delay relapse

Premalignant SOX2 overexpression in the fallopian tubes of ovarian cancer patients: Discovery and validation studies

Current screening methods for ovarian cancer can only detect advanced disease. Earlier detection has proved difficult because the molecular precursors involved in the natural history of the disease are unknown. To identify early driver mutations in ovarian cancer cells, we used dense whole genome sequencing of micrometastases and microscopic residual disease collected at three time points over three years from a single patient during treatment for high-grade serous ovarian cancer (HGSOC). The functional and clinical significance of the identified mutations was examined using a combination of population-based whole genome sequencing, targeted deep sequencing, multi-center analysis of protein expression, loss of function experiments in an in-vivo reporter assay and mammalian models, and gain of function experiments in primary cultured fallopian tube epithelial (FTE) cells. We identified frequent mutations involving a 40 kb distal repressor region for the key stem cell differentiation gene SOX2. In the apparently normal FTE, the region was also mutated. This was associated with a profound increase in SOX2 expression (p < 2−16), which was not found in patients without cancer (n = 108). Importantly, we show that SOX2 overexpression in FTE is nearly ubiquitous in patients with HGSOCs (n = 100), and common in BRCA1-BRCA2 mutation carriers (n = 71) who underwent prophylactic salpingo-oophorectomy. We propose that the finding of SOX2 overexpression in FTE could be exploited to develop biomarkers for detecting disease at a premalignant stage, which would reduce mortality from this devastating disease