BRCA mutational status shapes the stromal microenvironment of pancreatic cancer linking clusterin expression in cancer associated fibroblasts with HSF1 signaling

Abstract

Tumors initiate by mutations in cancer cells, and progress through interactions of the cancer cells with non-malignant cells of the tumor microenvironment. Major players in the tumor microenvironment are cancer-associated fibroblasts (CAFs), which support tumor malignancy, and comprise up to 90% of the tumor mass in pancreatic cancer. CAFs are transcriptionally rewired by cancer cells. Whether this rewiring is differentially affected by different mutations in cancer cells is largely unknown. Here we address this question by dissecting the stromal landscape of BRCA-mutated and BRCA Wild-type pancreatic ductal adenocarcinoma. We comprehensively analyze pancreatic cancer samples from 42 patients, revealing different CAF subtype compositions in germline BRCA-mutated vs. BRCA Wild-type tumors. In particular, we detect an increase in a subset of immune-regulatory clusterin-positive CAFs in BRCA-mutated tumors. Using cancer organoids and mouse models we show that this process is mediated through activation of heat-shock factor 1, the transcriptional regulator of clusterin. Our findings unravel a dimension of stromal heterogeneity influenced by germline mutations in cancer cells, with direct implications for clinical research.

Mapping the tumor stress network reveals dynamic shifts in the stromal oxidative stress response

“…We stained human tumor microarrays (TMAs) derived from four tumor types - breast, pancreas, ovary, and prostate - with antibodies for three stress transcription factors (TFs): NRF2 (Nuclear factor erythroid 2- related factor 2), a key factor of the oxidative stress response (OSR); ATF4 (Activating transcription factor 4), a master regulator of the unfolded protein stress response (UPR) and the integrated stress response; and HSF1 (Heat shock factor 1), which orchestrates the heat shock stress response (HSR) (Figure 1A). These TFs translocate to the nucleus upon activation and therefore their localization can be used as a proxy to monitor activation (Shaashua et al , 2022). Non- immune stromal cells were identified by negative staining for CD45 (immune cells) and CK (epithelial cells).…”

Transcriptome analysis reveals differences in cell cycle, growth and migration related genes that distinguish fibroblasts derived from pre-invasive and invasive breast cancer

“…These data indicate that molecular subtype may be a stronger influencing factor than stage, but it is not the only factor influencing stromal gene expression. Biological factors such as genetics, age and breast density ( 45 – 47 ) and lifestyle factors such as diet ( 48 ) could potentially affect gene expression and contribute to heterogeneity of fibroblasts within groups. These same factors as well as technical factors in isolation and culture of fibroblasts and platforms used could have contributed to overall differences between our experimental dataset and published datasets.…”

Regulation of HSF1 transcriptional complexes under proteotoxic stress

“…Importantly, the formation of HSF1 transcriptional complexes is closely associated with stress-related diseases, 6 including various types of cancers. 89,[206][207][208][209] HSF1 is activated in unstressed cancer cells and constitutively binds to target genes at higher levels. The interaction between HSF1 and RPA1 is required for the proliferation and tumor formation of melanoma cells, 74 and the blockade of HSF1-S419 phosphorylation is sufficient to inhibit tumor formation.…”

“…Most of the mechanisms proposed in this review could be commonly used in mammalian cells, but their impacts on HSP expression in different cell types or under different stress conditions may differ and should be determined, too. Importantly, the formation of HSF1 transcriptional complexes is closely associated with stress‐related diseases, 6 including various types of cancers 89 , 206–209 . HSF1 is activated in unstressed cancer cells and constitutively binds to target genes at higher levels.…”