The aim of this study was to analyze the alterations of PTCH1 (deletion/promoter methylation/mutation/expression) during the development of cervical cancer (CACX). For this purpose, deletion/methylation of PTCH1 were analyzed in HPV16 positive exfoliated asymptomatic cervical swabs (n = 74), cervical intraepithelial neoplasia (CIN) (n = 32), CACX (n = 174) samples, and two CACX cell lines. The deletion of PTCH1 increased significantly from CIN (11.5%) to stage I/II (42%) and comparable in stage III/IV (46%). Low frequency (14-16%) of PTCH1 methylation was seen in the asymptomatic exfoliated cervical cells and in the normal epithelium adjacent to the tumor followed by a significant increase in CIN (31%) to stage I/II (57%) and comparable in stage III/IV (58%). The overall alterations (deletion/methylation) of PTCH1 significantly increased from CIN (34%) to stage I/II (70%) and comparable in stage III/IV (69%). Interestingly, in the normal epithelium, methylation of PTCH1 was high in basal/parabasal layers (83%), followed by decrease in the spinous layer (33 %), and showed significant inverse correlation with its expression. Reduced expression of PTCH1 seen in tumors showed a significant association with its alterations (deletion/methylation). The expression pattern of PTCH1 showed an inverse correlation with the nuclear expression of GLI1 in the normal epithelium as well as in the tumors. High nuclear expression of HPV16, E6, and E7 were seen in basal/parabasal layers of the normal epithelium and also in tumors. The PTCH1 alterations (deletion and/or methylation) in tumors and its methylation in adjacent normal epithelium were associated with poor prognosis of patients. Thus, our data suggests that activation of the Hedgehog pathway due to PTCH1 inactivation along with HPV infection is important in CACX development.
To understand the mechanism of cellular stress in basal-parabasal layers of normal cervical epithelium and during different stages of cervical carcinoma, we analyzed the alterations (expression/methylation/copy number variation/mutation) of HIF-1α and its associated genes LIMD1, VHL and VEGF in disease-free normal cervix ( = 9), adjacent normal cervix of tumors ( = 70), cervical intraepithelial neoplasia (CIN; = 32), cancer of uterine cervix (CACX; = 174) samples and two CACX cell lines. In basal-parabasal layers of normal cervical epithelium, LIMD1 showed high protein expression, while low protein expression of VHL was concordant with high expression of HIF-1α and VEGF irrespective of HPV-16 (human papillomavirus 16) infection. This was in concordance with the low promoter methylation of LIMD1 and high in VHL in the basal-parabasal layers of normal cervix. LIMD1 expression was significantly reduced while VHL expression was unchanged during different stages of cervical carcinoma. This was in concordance with their frequent methylation during different stages of this tumor. In different stages of cervical carcinoma, the expression pattern of HIF-1α and VEGF was high as seen in basal-parabasal layers and inversely correlated with the expression of LIMD1 and VHL. This was validated by demethylation experiments using 5-aza-2'-deoxycytidine in CACX cell lines. Additional deletion of LIMD1 and VHL in CIN/CACX provided an additional growth advantage during cervical carcinogenesis through reduced expression of genes and associated with poor prognosis of patients. Our data showed that overexpression of HIF-1α and its target gene VEGF in the basal-parabasal layers of normal cervix was due to frequent inactivation of VHL by its promoter methylation. This profile was maintained during different stages of cervical carcinoma with additional methylation/deletion of VHL and LIMD1.
Single nucleotide polymorphisms (SNPs) in the 3'-UTR region are emerging cis-regulatory factors associated with the occurrences of several human diseases. SH3GL2, which is located at chromosome 9p21-22, is associated with hyperplastic/mildly dysplastic lesions of the head and neck and has a long 3'-UTR with multiple SNPs. The aim of the present study was to determine the susceptible allele(s) in the 3'-UTR SNPs of SH3GL2 in head and neck squamous cell carcinoma (HNSCC). First, we screened the genotypes of all SNPs located in the 3'-UTR of SH3GL2 in 110 controls and 147 cases in Indian populations by sequencing. A SNP (rs1049430:>G/T) that showed only heterozygosity was further confirmed by genotyping with an Illumina GoldenGate platform in 530 controls and 764 cases. Genotype-specific survival analysis of the HNSCC patients was performed. In addition, genotype-specific mRNA stability, isoform expression and protein expression were analyzed. SNP rs1049430 was not associated with disease occurrence, but it was associated with poor patient outcome. The G allele was associated with decreased SH3GL2 mRNA stability, differential splicing and low protein expression. Thus, our data demonstrate that the presence of the susceptible G allele in SNP rs1049430 is associated with the inactivation of SH3GL2 and could be used as a prognostic marker of HNSCC.
To understand the molecular mechanism of RB1 phosphorylation in basal-parabasal layers of normal cervix and during cervical cancer (CACX) development, we analyzed the alterations (expression/methylation/deletion/mutation) of RB1/phosphorylated RB1 (p-RB1) (ser807/811 and ser567) and two RB1 phosphorylation inhibitors, P16 and RBSP3, in disease-free normal cervical epithelium (n = 9), adjacent normal cervical epithelium of tumors (n = 70), cervical intraepithelial neoplasia (CIN; n = 28), CACX (n = 102) samples and two CACX cell lines. Immunohistochemical analysis revealed high/medium expression of RB1/p-RB1 (ser807/811 and ser567) and low expression of P16 and RBSP3 in proliferating basal-parabasal layers of majority of normal cervical epitheliums, irrespective of HPV16 infection. Interestingly, 35-52% samples showed high/medium expression of P16 in basal-parabasal layers of normal and had significant association with deleterious non-synonimous SNPs of P16. Methylation of P16 and RBSP3 in basal-parabasal layers of normal cervix (32 and 62%, respectively) showed concordance with their respective expressions in basal-parabasal layers. The methylation frequency of P16 and RBSP3 in basal-parabasal layers of normal did not change significantly in CIN and CACX. The deletion frequency of P16 and RB1 increased significantly with CACX progression. While, deletion of RBSP3 was high in CIN and comparable during CACX progression. P16 showed scattered and infrequent mutation in CACX. The alteration of P16 and RBSP3 was synergistic and showed association with overexpression of p-RB1 in tumors and associated with poor prognosis of patients. Thus, our data suggest that overexpression of p-RB1 in basal-parabasal layers of normal cervical epithelium was due to methylation/low functional-linked non-synonimous SNPs of P16 and RBSP3. This pattern was maintained during cervical carcinogenesis by additional deletion/mutation.
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