Skin fibroblasts from humans predisposed to colon cancer are not abnormally sensitive to DNA damaging agents

Colon fibroblasts from Pirc rats (F344/NTac-Apcam1137 ) exhibit a proliferative and inflammatory phenotype that could support early stages of colon carcinogenesis

The role of fibroblast APC mutation in carcinogenesis is not clear. Apc^+/− colon fibroblasts have been previously characterized: however, little is known about their behavior at very early‐stage of colon carcinogenesis. We cultured colon mucosa fibroblasts (PCF, Apc^+/−) of Pirc rats (F344/NTac‐Apc^am1137) at an early stage of tumorigenesis, in absence of preneoplastic lesions, and of age‐matched wt (WCF): DNA damage levels, inflammatory phenotype and the expression of known markers of CAFs were analyzed. The latter were also assessed by microarray analysis on colon normal mucosa of Pirc and wt animals. PCF exhibited higher proliferative rates (P < .001) and delayed replicative senescence onset (P < .05) compared to WCF, along with a lower level of oxidative DNA damage (P < .05). Furthermore, a constitutively higher expression of COX‐2 and sensitivity to inflammatory stimuli was found in PCF compared to WCF (P < .05), accompanied by higher invasive capability (P < .05) and presence of cytoplasmic chromatin foci (cytoplasmic chromatin foci, P < .05). However, they neither expressed CAFs markers (α‐SMA, IL‐6) nor responded to CAFs activating stimuli (TGF‐β). Accordingly, CAFs markers and activating stimuli resulted down‐regulated in Pirc normal mucosa compared to wt, whereas DNA damage response and tolerance pathways were overexpressed. These data show for the first time that a proliferative and inflammatory phenotype characterizes Apc^+/− colon fibroblasts since very early stages of colon tumorigenesis, and indicate a role of Apc mutation in driving fibroblast phenotypic alterations that could support the establishment of a protumorigenic environment. Early pharmacological targeting of these dysfunctions might impact on tumor prevention in FAP patients.

What's new?

Heterozygous mutations in APC represent the earliest event in sporadic colorectal carcinogenesis onset and cause familial adenomatous polyposis syndrome. However, the role of APC‐mutated fibroblasts remains unclear. Here, Apc^+/‐ fibroblasts isolated from apparently‐normal colon tissue of Pirc rats showed proliferative, inflammatory features and resistance to oxidative DNA damage, although they did not show cancer‐associated fibroblast features. These data suggest that, at the very early stages of colon tumourigenesis, Apc‐mutated colon fibroblasts favour the establishment of a pro‐tumourigenic environment for pre‐neoplastic lesion development. Early pharmacological targeting of these dysfunctions might be valuable for tumour prevention in familial adenomatous polyposis patients.

Altered transcriptome signature of phenotypically normal skin fibroblasts heterozygous for CDKN2A in familial melanoma: relevance to early intervention

Familial melanoma (FM) is a dominantly heritable cancer that is associated with mutations in the tumor suppressor CDKN2A/p16. In FM, a single inherited “hit” occurs in every somatic cell, enabling interrogation of cultured normal skin fibroblasts (SFs) from FM gene carriers as surrogates for the cell of tumor origin, namely the melanocyte. We compared the gene expression profile of SFs from FM individuals with two distinct CDKN2A/p16 mutations (V126D-p16 and R87P-p16) with the gene expression profile of SFs from age-matched individuals without p16 mutations and with no family history of melanoma. We show an altered transcriptome signature in normal SFs bearing a single-hit inherited mutation in the CDKN2A/p16 gene, wherein some of these abnormal alterations recapitulate changes observed in the corresponding cancer. Significantly, the extent of the alterations is mutation-site specific with the R87P-p16 mutation being more disruptive than the V126D-p16 mutation. We also examined changes in gene expression after exposure to ultraviolet (UV) radiation to define potential early biomarkers triggered by sun exposure. UV treatment of SFs from FM families induces distinct alterations in genes related to cell cycle regulation and DNA damage responses that are also reported to be dysregulated in melanoma. Importantly, these changes were diametrically opposed to UV-induced changes in SF from normal controls. We posit that changes identified in the transcriptome of SF from FM mutation carriers represent early events critical for melanoma development. As such, they may serve as specific biomarkers of increased risk as well as molecular targets for personalized prevention strategies in high-risk populations.

Cellular radiosensitivity of patients with different types of neurofibromatosis

Skin fibroblast cell strains were developed from nine Saudi patients with different types of neurofibromatosis (NF) and nine healthy subjects (controls), and their radiosensitivity was compared following chronic exposure to gamma-radiation at a dose rate of 0.0076 Gy/min (1 Gy = 100 rads). Cells from both normal appearing skin and café-au-lait spots of the different NF patients (7 out of 9) clearly showed increased radiosensitivity, with D10 (dose resulting in 10% survival) values of 2.0-4.4 Gy for the former and 3.0-4.8 Gy for the latter, compared to the normal controls (with D10 values of 6.1-10.6 Gy). These data provide further evidence of an association of enhanced cellular sensitivity to chronic irradiation with NF regardless of the classes they belong to. Hypersensitivity to specific carcinogens may, thus, be a factor responsible for the increased propensity to cancer in these patients.

Comparison of radiation-induced chromosomal damage between normal individuals and patients with familial polyposis coli

Cultured leukocytes of peripheral blood obtained from normal, healthy individuals and from patients with familial polyposis coli (FP) were exposed to 0 rads or 300 rads of 137Cs gamma radiation at G0 to compare damage in these two groups. Only cells in the first mitotic division were considered. The average chromosomal damage in the FP patients was not significantly higher than that in the normal group. The induced chromosomal damage at G0 was normally distributed in both the control and the patient groups as well as when they were combined.

The transformed (initiated) human cell phenotype: study of cultured skin fibroblasts from individuals predisposed to cancer

The present study demonstrated the expression of abnormal phenotypes (biomarkers) in cultured skin fibroblasts from hereditary adenomatosis of the colon and rectum (ACR) and neurofibromatosis (NF) patients. These biomarkers occur systemically and they include cytoskeletal structures, cytotoxicity and sensitivity to transformation by oncogenic agents, expression of transformation-associated antigen, and effects by a tumor promoter. Collectively, these biomarkers define the transformed (initiated) human cell phenotype, as determined through use of cultured skin fibroblasts that were obtained from individuals at risk of cancer. In conjunction with clinical signs, these biomarkers can be used to determine gene expression and gene penetrance. Extension of these studies in the form of a multiparameter matrix may permit the early detection of cancer.

Enhanced radiotolerance to ionizing radiation is correlated with increased cancer proneness of cultured fibroblasts from precursor states in neurofibromatosis patients

We have determined the sensitivity to gamma rays of cultured fibroblasts derived from clinically defined areas on the skin of neurofibromatosis patients. Fibroblasts from skin of normal appearance were normally sensitive to gamma irradiation. Significantly, however, fibroblasts from café-au-lait lesions and from neurofibromas were abnormally radiotolerant (about twofold) to treatment with gamma rays. This was seen in specimens taken from the same patient, as well as from different patients, within four different neurofibromatosis pedigrees. In contrast, no differences in radiosensitivity have been observed between fibroblasts derived from skin of normal appearance and those obtained from melanotic freckles of individuals with no family history of cancer. The results suggest that increased propensity to cancer in this cell system is associated with increased radiotolerance to ionizing radiation.

An imbalance in sex chromosomes alters cell survival of human skin fibroblasts exposed to ionizing radiation in vitro

We report that a cell clone with a 45,X(-Y) karyotype, obtained from a male individual who is a gene carrier for hereditary adenomatosis of the colon and rectum (ACR), was considerably more resistent to gamma-ray irradiation (D0 range 184-240) than were diploid ACR skin fibroblasts (SF) obtained from sister biopsies of the same individual or of normal controls (D0 range 90-125). In addition, cell clones obtained from a Turner's syndrome female patient and from a female patient with focal endometrial hyperplasia, each with a 45,X(-X) karyotype, were abnormally resistent to gamma-ray irradiation (D0 range 168-195). These results may suggest an association between the status of the sex chromosomes and an altered response to gamma-ray-induced cytotoxicity of human SF.