Tumorigenic Responses of Cancer-Associated Stromal Fibroblasts after Ablative Radiotherapy: A Transcriptome-Profiling Study

Abstract

<p> <span>Cancer-associated fibroblasts (CAFs) are key elements in the progression of cancer and thereby represent important targets for cancer therapies. Increased attention has been given to ablative radiotherapy in the clinics. Therefore, in this study we have aimed at identifying the transcriptional responses occurring in primary CAFs exposed to high-dose irradiation. Established primary CAFs obtained from non-small-cell lung cancer (NSCLC) patient material were irradiated with a single dose of 18 Gy and total RNA was isolated 24 hrs after treatment. Radiation-induced transcriptional alterations were investigated by gene expression analysis using genome-wide microarrays. Obtained results were verified by qRT-PCR of relevant genes. Confirmation of gene expression outcomes was achieved by diverse functional and expression assays including DNA damage response, measurements of reactive oxygen species (ROS) by flow cytometry and senescence-associated <i>β</i>-galactosidase. Irradiation resulted in differential expression of 680 genes of which 557 were up- and 127 down-regulated. Of those, 153 genes were differentially expressed with a fold-change greater than 1.0 and an adjusted p-value less than 0.05 across different comparisons (non-irradiated vs. irradiated). Expression patterns revealed profound changes in biological functions and processes involved in DNA repair, apoptosis, p53 pathway, autophagy, senescence, ROS production and immune response. CAFs display pro- and anti-tumorigenic effects after having received a single high-dose radiation. The measured effects will have an impact on the tumor microenvironment in respect to tumor growth and metastasis.</span><span></span> </p> <p> <span></span> </p

Low Mast Cell Density Predicts Poor Prognosis in Oral Squamous Cell Carcinoma and Reduces Survival in Head and Neck Squamous Cell Carcinoma

“…Such radiotherapy-activated CAFs may, therefore, actually facilitate disease recurrence e.g. through increased amphiregulin production (29) or induction of radiotherapy resistance (30). This was also supported by the observation that patients with increased CAF density treated with surgery only had fewer relapses than those with few CAFs.…”

“…CAFs survive low-dose (1.8 Gy) but not 3.6 Gy radiation (28,29). The patients of the current study received sequential 2 Gy doses postoperatively, which might not kill CAFs, but merely induce a stress response (29). Such radiotherapy-activated CAFs may, therefore, actually facilitate disease recurrence e.g.…”

“…Radiotherapy may activate CAFs to produce tumorstimulating factors (27). CAFs survive low-dose (1.8 Gy) but not 3.6 Gy radiation (28,29). The patients of the current study received sequential 2 Gy doses postoperatively, which might not kill CAFs, but merely induce a stress response (29).…”

Ionizing radiation abrogates the pro-tumorigenic capacity of cancer-associated fibroblasts co-implanted in xenografts

“…Of interest, simultaneous irradiation of normal fibroblasts and murine (adenocarcinoma) lung tumor cells in co-culture reportedly was abrogating the pro-migratory phenotype of these carcinoma cells 57 . Others have performed transcriptome studies, comparing irradiated and non-irradiated fibroblasts, and have thus revealed profound changes in biological functions and processes involved in DNA repair, activation of stress responses, cell cycle arrest, senescence-associated genes, autophagy regulatory elements, ROS production and immune responses 54 58 59 . Our group has previously shown that irradiated lung-CAFs become prematurely senescent (80% rate by 1 × 18 Gy, 50% rate by 6 × 3 Gy), slow down their proliferative rate, and display reduced migratory function 24 .…”

Radiation-Induced Transformation of Immunoregulatory Networks in the Tumor Stroma

“…Moreover, CAFs express cytokines and chemokines that support the recruitment and maintenance of immunosuppressive myeloid cells, promote the polarization of macrophages toward the M2-phenotype, and interfere with maturation of DCs ( 109 ). In the context of RT, CAFs are considered to be very radioresistant ( 62 , 110 – 112 ), however, exposure to IR is able to induce cellular senescence in fibroblasts, especially at doses above 12 Gy ( 62 ). In xenograft models, senescent fibroblasts co-transplanted with cancer cells have been found to increase tumorigenicity.…”