Abstract
Background and AimsSporadic colorectal cancer (CRC) development is a sequential process showing age-dependency, uncontrolled epithelial proliferation and decreased apoptosis. During juvenile growth cellular proliferation and apoptosis are well balanced, which may be perturbed upon aging. Our aim was to correlate proliferative and apoptotic activities in aging human colonic epithelium and colorectal cancer. We also tested the underlying molecular biology concerning the proliferation- and apoptosis-regulating gene expression alterations.Materials and MethodsColorectal biopsies from healthy children (n1 = 14), healthy adults (n2 = 10), adult adenomas (n3 = 10) and CRCs (n4 = 10) in adults were tested for Ki-67 immunohistochemistry and TUNEL apoptosis assay. Mitosis- and apoptosis-related gene expression was also studied in healthy children (n1 = 6), adult (n2 = 41) samples and in CRC (n3 = 34) in HGU133plus2.0 microarray platform. Measured alterations were confirmed with RT-PCR both on dependent and independent sample sets (n1 = 6, n2 = 6, n3 = 6).ResultsMitotic index (MI) was significantly higher (p<0.05) in intact juvenile (MI = 0.33±0.06) and CRC samples (MI = 0.42±0.10) compared to healthy adult samples (MI = 0.15±0.06). In contrast, apoptotic index (AI) was decreased in children (0.13±0.06) and significantly lower in cancer (0.06±0.03) compared to healthy adult samples (0.17±0.05). Eight proliferation- (e.g. MKI67, CCNE1) and 11 apoptosis-associated genes (e.g. TNFSF10, IFI6) had altered mRNA expression both in the course of normal aging and carcinogenesis, mainly inducing proliferation and reducing apoptosis compared to healthy adults. Eight proliferation-associated genes including CCND1, CDK1, CDK6 and 26 apoptosis-regulating genes (e.g. SOCS3) were differently expressed between juvenile and cancer groups mostly supporting the pronounced cell growth in CRC.ConclusionColorectal samples from children and CRC patients can be characterized by similarly increased proliferative and decreased apoptotic activities compared to healthy colonic samples from adults. Therefore, cell kinetic alterations during colorectal cancer development show uncontrolled rejuvenescence as opposed to the controlled cell growth in juvenile colonic epithelium.
Highlights
The normal cell renewal of the healthy colonic epithelium takes about 5 days, through cell proliferation, differentiation and apoptosis
Eight proliferation- (e.g. MKI67, CCNE1) and 11 apoptosis-associated genes (e.g. TNFSF10, IFI6) had altered mRNA expression both in the course of normal aging and carcinogenesis, mainly inducing proliferation and reducing apoptosis compared to healthy adults
Colorectal samples from children and colorectal cancer (CRC) patients can be characterized by increased proliferative and decreased apoptotic activities compared to healthy colonic samples from adults
Summary
The normal cell renewal of the healthy colonic epithelium takes about 5 days, through cell proliferation, differentiation and apoptosis. The regulation of proliferative and apoptotic mechanisms may alter during normal aging and colorectal carcinogenesis. Aging is a physiologic mechanism that begins after conception It affects almost every cell in the organism with the possible exception of stem cells and tumor cells. In aged animal populations increased cell proliferation and decreased apoptosis in colonic epithelium was observed and thought to facilitate uncontrolled cell proliferation and tumorigenesis, which might explain the higher incidence of colorectal cancer in the elderly human [8]. Sporadic colorectal cancer (CRC) development is a sequential process showing age-dependency, uncontrolled epithelial proliferation and decreased apoptosis. Our aim was to correlate proliferative and apoptotic activities in aging human colonic epithelium and colorectal cancer. We tested the underlying molecular biology concerning the proliferation- and apoptosis-regulating gene expression alterations
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