RESUMO
Expression of the epidermal growth factor ligands amphiregulin (AREG) and epiregulin (EREG) is positively correlated with a response to EGFR-targeted therapies in colorectal cancer. Gene-body methylation sites, which show a strong inverse correlation with AREG and EREG gene expression, were identified in cell lines using targeted 454 FLX-bisulfite sequencing and SIRPH analyses for AREG/EREG promoters and intragenic CpGs. Upon treatment of colorectal cancer cells with 5-aza-2'-desoxycytidine, methylation decreases at specific intragenic CpGs accompanied by upregulation of AREG and EREG gene expression. The same AREG gene-body methylation was also found in human colorectal cancer samples and is independent of KRAS and NRAS mutations. Methylation is specifically decreased in the tumor epithelial compartment as compared to stromal tissue and normal epithelium. Investigation of a promoter/enhancer function of the AREG exon 2 region revealed a potential promoter function in reverse orientation. Retrospective comparison of the predictive power of AREG gene-body methylation versus AREG gene expression using samples from colorectal cancer patients treated with anti-EGFR inhibitors with complete clinical follow-up revealed that AREG expression is superior to AREG gene methylation. AREG and EREG genes undergo a complex regulation involving both intragenic methylation and promoter-dependent control.
Assuntos
Anfirregulina/genética , Neoplasias Colorretais/genética , Epirregulina/genética , Anfirregulina/biossíntese , Células CACO-2 , Linhagem Celular Tumoral , Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Metilação de DNA , Epigênese Genética , Células Epiteliais/metabolismo , Células Epiteliais/patologia , Receptores ErbB/genética , Receptores ErbB/metabolismo , Expressão Gênica , Células HCT116 , Humanos , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Estudos Retrospectivos , Células Estromais/metabolismo , Células Estromais/patologiaRESUMO
Based on a dataset comprising coding DNA sequences of 23 anthropoid primates, we herein investigate if rates of sequence evolution of SPerm Adhesion Molecule1 (SPAM1, also PH-20), which participates in sperm-egg interaction, is lower in more sexually dimorphic species. For comparison, we analyze sequence evolution of apolipoproteinA-IV (APOA4) and apolipoprotein A-V (APOA5), which should evolve under less or even no sexual selection given their expression in blood, digestive tract, liver, and lungs. Regression analyses provides significant support for a negative dependence of SPAM1 derived branch-specific ratios of non-synonymous to synonymous substitution rates (dN/dS) on sexual size dimorphism (SSD) in a subsample comprising New World and Old World monkeys. We moreover observed a tendency for a positive correlation of substitution rates of SPAM1 with relative testes weight (RTW) and significantly lowered dN/dS estimates in uni-male and uni-male/multi-male breeding monkeys. Importantly, the pattern was not reproduced when analyzing partial APOA4 and APOA5 sequences. These findings illustrate that different levels of sperm competition, probably fueled by female cryptic choice, account for species-specific sequence evolution of SPAM1 in monkeys. Remarkably, present data do not support a correlation of species-specific sequence evolution of SPAM1 with sexual selection levels in hominoids (apes including humans). This can partly be ascribed to a relaxation of functional constraint of SPAM1 in some hominoid species. Additional factors confounding regression analyses specifically in hominoids might be higher levels of sperm competition than reflected by SSD and RTW in some species, a rather strong effect of female mate choice on paternity rates in others, and - in particular in humans - socio-cultural factors not measurable by SSD and RTW.