Abstract
Telomerase activity contributes to cell immortalization by avoiding telomere shortening at each cell division; indeed, its catalytic subunit telomerase reverse transcriptase (TERT) is overexpressed in many tumors, including human oral squamous cell carcinoma (hOSCC). In these tumors, matrix metalloproteinases (MMPs), a group of zinc-dependent endopeptidases involved in cell migration, contribute to invasive potential of cancer cells. A proportion of hOSCC is associated with infection by high-risk human papillomavirus (HR-HPVs), whose E6 oncogene enhances TERT and MMPs expression, thus promoting cancer progression. Feline oral squamous cell carcinoma (FOSCC) is a malignant tumor with highly invasive phenotype; however, studies on telomerase activity, TERT, and MMPs expression are scarce. In this study, we demonstrate telomerase activity, expression of TERT, and its transcriptional activator cMyc along with expression of MMP-1, -2, and -9 in FOSCC-derived cell lines SCCF2 and SCCF3, suggesting a contribution by these pathways in cell immortalization and invasion in these tumors. Recent studies suggest that a sub-group of FOSCC as well as SCCF2 and SCCF3 are associated with Felis catus PV type-2 (FcaPV-2) infection. However, in this work, FcaPV-2 E6 gene knock-down caused no shift in either TERT, cMyc, or MMPs levels, suggesting that, unlike its human counterpart, the viral oncogene plays no role in their regulation.
Highlights
Telomerase is a ribonucleoprotein enzyme complex whose main function is to extend telomeric DNA by adding repetitive sequences of six nucleotides (5′-TTAGGG-3′) at telomere ends [1]
Telomerase reverse transcriptase (TERT) and cMyc cDNA were successfully amplified in both cell lines by Quantitative PCR (qPCR); relative quantization analysis revealed lower TERT gene expression but higher cMyc relative mRNA levels in SCCF3 compared to SCCF2 (Figures 1A,B)
The data obtained by Western blotting (WB) followed by densitometric analysis yielded consistent results, showing lower TERT protein expression but higher cMyc protein amounts in SCCF3 with respect to SCCF2 (Figures 1C–E)
Summary
Telomerase is a ribonucleoprotein enzyme complex whose main function is to extend telomeric DNA by adding repetitive sequences of six nucleotides (5′-TTAGGG-3′) at telomere ends [1]. Telomerase reverse transcriptase (TERT) is the catalytic subunit and its activity consists in adding this six-nucleotide repeat using the RNA template (TR) included in the holoenzyme [1]. Telomerase activity is prominent in cells that must keep a high proliferative potential, such as stem cells and, importantly, neoplastic cells [1]. TERT is expressed in most cancers, including human oral squamous cell carcinoma (hOSCC) [2]. In these tumors, telomerase activity contributes to cellular immortalization, playing a key role in neoplastic process and representing a marker of poor prognosis [3, 4]. HPV-16 may contribute to activation of telomerase through viral oncoprotein E6, which is able to enhance TERT expression and increase enzymatic activity by different mechanisms such as promoter activation or epigenetic or post-transcriptional regulation [1]
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