High Positive Correlations between ANRIL and p16-CDKN2A/p15-CDKN2B/p14-ARF Gene Cluster Overexpression in Multi-Tumor Types Suggest Deregulated Activation of an ANRIL–ARF Bidirectional Promoter

Abstract

The <i>CDKN2B-AS1</i> gene, also called <i>ANRIL</i>, is located at the human <i>CDKN2A/B</i> locus at 9p21.3 and transcribed by RNA polymerase II into a long non-coding RNA of 3834 bp. The <i>CDKN2B-AS1</i> gene overlaps a critical region of 125 kb covering the <i>CDKN2B</i> gene. The <i>CDKN2A/B</i> locus encompasses three major tumor suppressors juxtaposed and joined into a <i>p16-CDKN2A/p15-CDKN2B/p14-ARF</i> gene cluster. <i>CDKN2A</i> encodes splice variants p16-CDKN2A and p14-ARF, and <i>CDKN2B</i> encodes p15-CDKN2B. <i>ANRIL</i> shares a bidirectional promoter with the <i>p14-ARF</i> gene and is transcribed from the opposite strand to the cluster. We performed an analysis of the expression level of <i>ANRIL</i> and tumor suppressor <i>p16-CDKN2A, p15-CDKN2B</i>, and <i>p14-ARF</i> genes using quantitative RT-PCR in a multitumor panel. We observed the overexpression of the four genes <i>ANRIL</i>, <i>p16-CDKN2A, p15-CDKN2B</i>, and <i>p14-ARF</i> in the great majority of the 17 different cancer types. <i>ANRIL</i> was upregulated in 13/17 tumors compared to normal tissues, ranging from 5% (prostate cancer) to 91% (cervix cancer), with variable expression of <i>p16-CDKN2A, p15-CDKN2B</i>, and <i>p14-ARF</i> genes. A high positive correlation was identified between levels of expression of <i>ANRIL</i> and the three tumor suppressors. The strongest positive association was observed with <i>p14-ARF</i> (<i>p</i> < 0.001) in all but one (lung squamous cell carcinoma) of the examined tumor types. This correlation suggests coordinated deregulated mechanisms in all cancer types through aberrant activation of a bidirectional <i>p14-ARF/ANRIL</i> promoter. Furthermore, significant positive correlation was unexpectedly established in prostatic carcinomas, in contradiction with previous data.