NFκB (RelA) mediates transactivation of hnRNPD in oral cancer cells

Heterogeneous Ribonucleoprotein D (hnRNPD) is an RNA binding protein involved in post-transcriptional regulation of multiple mediators of carcinogenesis. We previously demonstrated a strong association of hnRNPD over expression with poor outcome in Oral Squamous Cell Carcinoma (OSCC). However, hitherto the precise molecular mechanism of its overexpression in oral cancer was not clear. Therefore, in an attempt to elucidate the transcriptional regulation of hnRNPD expression, we cloned 1406 bp of 5ʹ flanking region of human hnRNPD gene along with 257 bp of its first exon upstream to promoterless luciferase reporter gene in pGL3-Basic. Transfection of the resulting construct in SCC-4 cells yielded 1271 fold higher luciferase activity over parent vector. By promoter deletion analysis, we identified a canonical TATA box containing 126 bp core promoter region that retained ~ 58% activity of the full length promoter. In silico analysis revealed the presence of four putative NFκB binding motifs in the promoter. Sequential deletion of these motifs from the full-length promoter reporter construct coupled with luciferase assays revealed an 82% decrease in promoter activity after deletion of the first (−1358/−1347) motif and 99% reduction after the deletion of second motif (−1052/−1041). In-vivo binding of NFκB (RelA) to these two motifs in SCC-4 cells was confirmed by ChIP assays. Site directed mutagenesis of even one of these two motifs completely abolished promoter activity, while mutagenesis of the remaining two motifs had marginal effect on the same. Consistent with these findings, treatment of SCC-4 cells with PDTC, a known inhibitor of NFκB dramatically reduced the levels hnRNPD mRNA and protein. Finally, the expression of hnRNPD and NFκB in clinical specimen from 37 oral cancer patients was assessed and subjected to Spearmen’s Correlation analysis which revealed a strong positive correlation between the two. Thus, results of the present study for the first time convincingly demonstrate NFκB (RelA) mediated transcriptional upregulation of hnRNPD expression in oral cancer.

The frequency of high-risk human papillomavirus types, HPV16 lineages, and their relationship with p16INK4a and NF-κB expression in head and neck squamous cell carcinomas in Southwestern Iran

High-risk human papillomaviruses (hr-HPVs) are the key risk factors implicated in the development of a significant proportion of head and neck squamous cell carcinomas (HNSCCs). We aimed to investigate the distribution of hr-HPV types and HPV16 lineages in a sample of patients with HNSCC and the possible association between HPV status and the expression of P16INK4A and NF-κB in Iranian HNSCC patients. We examined 108 formalin-fixed, paraffin-embedded (FFPE) histologically confirmed primary SCC tissue specimens of different head and neck anatomical sites. HPV types and HPV16 lineages were determined by nested PCR and overlapping nested PCR assays, respectively, followed by gene sequencing and phylogenetic analysis. The expression of p16INK4a and NF-κB was evaluated by immunohistochemistry. Twenty-five (23.1%) HNSCC tissue specimens were tested positive for HPV infection. The most prevalent HPV type was HPV-16, followed by HPV18 and HPV11. HPV16 variants belonged to the lineage A and lineage D which were further sorted into sublineages A1, A2, and D2. A significant association between HPV status and p16INK4a immunoreactivity was observed in more than 76% of the HPV-related HNSCCs (P < 0.0001). The overexpression of p16INK4a and cytoplasmic NF-κB was more common in low-grade HNSCC tumors. Our data highlights that HPV16, in particular the A2 sublineage, followed by A1 and D2 sublineages are the major agents associated with HNSCCs in Iran. Based on HPV16 predominance and its lineage distribution pattern, it seems that the prophylactic vaccines developed for cervical cancer prevention could also be applicable for the prevention of HPV-related HNSCCs in our population.

Hypoxia induced EMT: A review on the mechanism of tumor progression and metastasis in OSCC

Hypoxia, a condition of low oxygen tension in tissues, has emerged as a crucial factor in tumor pathophysiology. Hypoxic microenvironment gives rise to altered cellular metabolism and triggers varied molecular responses. These responses promote tumor progression and confer radiation resistance and chemo resistance to tumors. The predominant molecules that are associated with hypoxia research are the hypoxia inducible factors (HIFs). HIFs are known to regulate a large group of genes that are involved in cell survival, proliferation, motility, metabolism, pH regulation, extracellular matrix function, inflammatory cell recruitment and angiogenesis by inducing the expression of their downstream target genes. The process of epithelial to mesenchymal transition (EMT) has been associated with metastasis in cancer. Reports also suggest that hypoxia triggers EMT in several types of cancer including breast cancer, prostate cancer and oral cancer. Oral cancer is a predominant cancer in Central and South East Asia. However, in the recent times, the incidence rates of oral cancer have been increasing in Northern and Eastern Europe as well. This review articulates the role of hypoxia and the associated factors like HIFs in inducing EMT in oral cancer (OSCC).