No abstract

Gastric cancer is the third most lethal cancer worldwide, and evaluation of the genomic status of gastric cancer cells has not translated into effective prognostic or therapeutic strategies.We therefore hypothesize that outcomes may depend on the tumor microenvironment (TME), in particular, cancerassociated fibroblasts (CAF). However, very little is known about the role of CAFs in gastric cancer. To address this, we mapped the transcriptional landscape of human gastric cancer stroma by microdissection and RNA sequencing of CAFs from patients with gastric cancer. A stromal gene signature was associated with poor disease outcome, and the transcription factor heat shock factor 1 (HSF1) regulated the signature. HSF1 upregulated inhibin subunit beta A and thrombospondin 2, which were secreted in CAF-derived extracellular vesicles to the TME to promote cancer. Together, our work provides the first transcriptional map of human gastric cancer stroma and highlights HSF1 and its transcriptional targets as potential diagnostic and therapeutic targets in the genomically stable tumor microenvironment. Significance: This study shows how HSF1 regulates a stromal transcriptional program associated with aggressive gastric cancer and identifies multiple proteins within this program as candidates for therapeutic intervention. better understand the molecular basis of this disease, and to identify 48 biomarkers that may predict outcome and guide therapy.49 Gastric cancer is a heterogeneous disease. Traditionally, anatomical 50 location (true gastric vs. gastro-esophageal) and histologic character-51 istics (diffuse vs. intestinal; tubular vs. papillary) have been used to 52 classify gastric cancer subtypes (2). Recent advances in molecular 53 understanding have enabled classification of gastric cancer into dif-54 ferent subtypes based on chromosomal instability, microsatellite 55 instability, genomic stability, presence of Epstein-Barr virus, and 56 epithelial-mesenchymal transition (EMT), which were associated with 57 different survival outcomes (3-6). Mutations in CDH1 and KRAS, and 58 overexpression of HER2, EGFR, FGFR2, VEGF, were shown to 59 contribute to disease progression and correlate with poor out-60 come (7, 8). Despite serving as valuable guides in deciphering the 61 complexity of gastric cancer, there has been little success in applying 62 these molecular classifiers to treatment stratification and development 63 of targeted therapies (3). Prognosis in the clinic is still mostly evaluated 64 on the basis of TNM staging (tumor size, lymph node involvement, and 65 metastasis), and the standard of care for localized gastric cancer is 66 surgical intervention combined with chemotherapy (7). 67 Increasing evidence over the past decade highlighted the indispens-68 able contribution of the tumor microenvironment (TME) to disease 69 progression and treatment resistance (9). The TME is comprised of 70 various cell types, including endothelial cells, fibroblasts, macro-71 phages, and lymphocytes, as well as extracellular matrix co...

In the colon, long-term exposure to chronic inflammation drives colitis-associated colon cancer (CAC) in patients with inflammatory bowel disease. While the causal and clinical links are well established, molecular understanding of how chronic inflammation leads to the development of colon cancer is lacking. Here we deconstruct the evolving microenvironment of CAC by measuring proteomic changes and extracellular matrix (ECM) organization over time in a mouse model of CAC. We detect early changes in ECM structure and composition, and report a crucial role for the transcriptional regulator heat shock factor 1 (HSF1) in orchestrating these events. Loss of HSF1 abrogates ECM assembly by colon fibroblasts in cell-culture, prevents inflammation-induced ECM remodeling in mice and inhibits progression to CAC. Establishing relevance to human disease, we find high activation of stromal HSF1 in CAC patients, and detect the HSF1-dependent proteomic ECM signature in human colorectal cancer. Thus, HSF1-dependent ECM remodeling plays a crucial role in mediating inflammation-driven colon cancer.

Metastasis is the main cause of cancer-related mortality. Despite intense efforts to understand the mechanisms underlying the metastatic process, treatment of metastatic cancer is still challenging. Here we describe a chemotherapy-induced, host-mediated mechanism that promotes remodeling of the extracellular matrix (ECM), ultimately facilitating cancer cell seeding and metastasis. Paclitaxel (PTX) chemotherapy enhanced rapid ECM remodeling and mechano-structural changes in the lungs of tumor-free mice, and the protein expression and activity of the ECM remodeling enzyme lysyl oxidase (LOX) increased in response to PTX. A chimeric mouse mode harboring genetic LOX depletion revealed chemotherapy-induced ECM remodeling was mediated by CD8+ T cells expressing LOX. Consistently, adoptive transfer of CD8+ T cells, but not CD4+ T cells or B cells, from PTX-treated mice to naïve immuno-deprived mice induced pulmonary ECM remodeling.Lastly, in a clinically relevant metastatic breast carcinoma model, LOX inhibition counteracted the metastasispromoting, ECM-related effects of PTX. This study highlights the role of immune cells in regulating ECM and metastasis following chemotherapy, suggesting that inhibiting chemotherapy-induced ECM remodeling represents a potential therapeutic strategy for metastatic cancer.

Tumors are supported by cancer-associated fibroblasts (CAFs). CAFs are heterogeneous and carry out distinct cancer-associated functions. Understanding the full repertoire of CAFs and their dynamic changes could improve the precision of cancer treatment. CAFs are usually analyzed at a single time-point using specific markers, and it is therefore unclear whether CAFs display plasticity as tumors evolve.Here, we analyze thousands of CAFs using index and transcriptional single-cell sorting, at several time-points along breast tumor progression in mice, uncovering distinct subpopulations. Strikingly, the transcriptional programs of these subpopulations change over time and in metastases, transitioning from an immune-regulatory program to wound healing and antigen-presentation programs, indicating that CAFs and their functions are dynamic. Two main CAF subpopulations are also found in human breast tumors, where their ratio is associated with disease outcome across subtypes, and is particularly correlated with BRCA mutations in triple-negative breast cancer. These findings indicate that the repertoire of CAFs changes over time in breast cancer progression, with direct clinical implications.