Cancer-Associated Fibroblasts Facilitate Squamous Cell Carcinoma Lung Metastasis in Mice by Providing TGFβ-Mediated Cancer Stem Cell Niche

Abstract

Cancer-associated fibroblasts (CAFs) have been shown to enhance squamous cell carcinoma (SCC) growth, but it is unclear whether they promote SCC lung metastasis. We generated CAFs from K15.KrasG12D.Smad4–/– mouse SCCs. RNA expression analyses demonstrated that CAFs had enriched transforming growth factor-beta (TGFβ) signaling compared to normal tissue-associated fibroblasts (NAFs), therefore we assessed how TGFβ-enriched CAFs impact SCC metastasis. We co-injected SCC cells with CAFs to the skin, tail vein, or the lung to mimic sequential steps of lung metastasis. CAFs increased SCC volume only in lung co-transplantations, characterized with increased proliferation and angiogenesis and decreased apoptosis compared to NAF co-transplanted SCCs. These CAF effects were attenuated by a clinically relevant TGFβ receptor inhibitor, suggesting that CAFs facilitated TGFβ-dependent SCC cell seeding and survival in the lung. CAFs also increased tumor volume when co-transplanted to the lung with limiting numbers of SCC cancer stem cells (CSCs). In vitro, CSC sphere formation and invasion were increased either with co-cultured CAFs or with CAF conditioned media (which contains the highest TGFβ1 concentration) and these CAF effects were blocked by TGFβ inhibition. Further, TGFβ activation was higher in primary human oral SCCs with lung metastasis than SCCs without lung metastasis. Similarly, TGFβ activation was detected in the lungs of mice with micrometastasis. Our data suggest that TGFβ-enriched CAFs play a causal role in CSC seeding and expansion in the lung during SCC metastasis, providing a prognostic marker and therapeutic target for SCC lung metastasis.

TGF-β signaling in the tumor metabolic microenvironment and targeted therapies

“…TGF-β signaling is one of the most important pathways influencing tumor initiation [ 37 ], growth [ 38 ], and metastasis [ 39 ]. Consistently, we observed that TGF-β activation is essential for lung metastasis growth in head and neck squamous cell carcinoma [ 40 ]. Currently, there are many agents designed to target TGF-β signaling that have achieved satisfying clinical cancer treatment efficacy [ 10 ].…”

“…CAFs are the most abundant stromal cells that promote cancer growth and metastasis [ 10 , 148 , 149 ]. Glucose metabolism reprogramming in CAFs is mainly involved in glycolysis and the TCA cycle.…”

Development of a Multicellular 3D Tumor Model to Study Cellular Heterogeneity and Plasticity in NSCLC Tumor Microenvironment

“…Similar to the in-vivo TME condition, the external microenvironment of in-vitro cell cultures also influences their gene expression pattern, metabolic requirements, and signalling pathways ( 33 ). For instance, co-culture of cancer cells with CAFs leads to the promotion of stem-cell-like properties in squamous cell carcinoma ( 34 ), cancer cells and their exosomes derived TGF-β augmented proliferation and expression of CAF markers ( 35 ), and the co-culture of pancreatic cancer cells with monocytes and fibroblasts induces the production of immunosuppressive cytokines which are known to promote polarization towards M2 like macrophages and myeloid-derived suppressive cells (MDSCs) ( 36 ). All these reports highlighted the importance of developing in-vitro tumorigenic 3D cultures to imitate the in-vivo TME features and establish tumor-stroma interaction.…”

Micro-RNAs, the Cornerstones of the Future of Radiobiology in Head and Neck Cancers?

“…Epidermal growth factor (EGFR) is involved in the control of multiple pathways that mediate both proliferation and invasion and migration. EGFR also modulates tumor survival and angiogenesis, and EGF-induced STAT3 signaling initiates the transcription of genes that modulate cell growth, survival, and angiogenesis (Cyclyn D1, Bcl-XL, and VEGF, respectively) [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Progression and metastasis involve the interaction of the tumor with the tumor microenvironment and the remodeling of it and the stromal cells, a cytokine-mediated interaction.…”