Simultaneous down-regulation of tumor suppressor genes RBSP3/CTDSPL, NPRL2/G21 and RASSF1A in primary non-small cell lung cancer

Abstract

BackgroundThe short arm of human chromosome 3 is involved in the development of many cancers including lung cancer. Three bona fide lung cancer tumor suppressor genes namely RBSP3 (AP20 region),NPRL2 and RASSF1A (LUCA region) were identified in the 3p21.3 region. We have shown previously that homozygous deletions in AP20 and LUCA sub-regions often occurred in the same tumor (P < 10-6).MethodsWe estimated the quantity of RBSP3, NPRL2, RASSF1A, GAPDH, RPN1 mRNA and RBSP3 DNA copy number in 59 primary non-small cell lung cancers, including 41 squamous cell and 18 adenocarcinomas by real-time reverse transcription-polymerase chain reaction based on TaqMan technology and relative quantification.ResultsWe evaluated the relationship between mRNA level and clinicopathologic characteristics in non-small cell lung cancer. A significant expression decrease (≥2) was found for all three genes early in tumor development: in 85% of cases for RBSP3; 73% for NPRL2 and 67% for RASSF1A (P < 0.001), more strongly pronounced in squamous cell than in adenocarcinomas. Strong suppression of both, NPRL2 and RBSP3 was seen in 100% of cases already at Stage I of squamous cell carcinomas. Deregulation of RASSF1A correlated with tumor progression of squamous cell (P = 0.196) and adenocarcinomas (P < 0.05). Most likely, genetic and epigenetic mechanisms might be responsible for transcriptional inactivation of RBSP3 in non-small cell lung cancers as promoter methylation of RBSP3 according to NotI microarrays data was detected in 80% of squamous cell and in 38% of adenocarcinomas. With NotI microarrays we tested how often LUCA (NPRL2, RASSF1A) and AP20 (RBSP3) regions were deleted or methylated in the same tumor sample and found that this occured in 39% of all studied samples (P < 0.05).ConclusionOur data support the hypothesis that these TSG are involved in tumorigenesis of NSCLC. Both genetic and epigenetic mechanisms contribute to down-regulation of these three genes representing two tumor suppressor clusters in 3p21.3. Most importantly expression of RBSP3, NPRL2 and RASSF1A was simultaneously decreased in the same sample of primary NSCLC: in 39% of cases all these three genes showed reduced expression (P < 0.05).

NPRL2 gene expression in the progression of colon tumors

“…The downregulation rate in our study is similar to the levels observed in HCC and esophageal squamous cell carcinoma (ESCC), but it is lower than the rates described for NSCLC (Yi-Lo et al, 2006;Otani et al, 2009;Senchenko et al, 2010). Senchenko et al (2010) reported NPRL2 downregulation in 73% of all NSCLC cases. However, downregulation of NPRL2 was significantly different between squamous cell tumors (85%) and adenocarcinomas (44%) in the NSCLC patients.…”

“…We observed a decrease in NPRL2 mRNA level in 45.45% of the colon cancer patients. Downregulation of NPRL2 has been reported for some cancers such as non-smallcell lung carcinoma (NSCLC), hepatocellular carcinoma (HCC), and esophageal squamous cell carcinoma at different frequencies (Yi-Lo et al, 2006;Otani et al, 2009;Senchenko et al, 2010). The downregulation rate in our study is similar to the levels observed in HCC and esophageal squamous cell carcinoma (ESCC), but it is lower than the rates described for NSCLC (Yi-Lo et al, 2006;Otani et al, 2009;Senchenko et al, 2010).…”

Novel tumor suppressor candidates on chromosome 3 revealed by NotI-microarrays in cervical cancer

“…Earlier, we demonstrated simultaneous inactivation of some genes from this 3p21.3 region, including RASSF1A, RBSP3 and ITGA9 in lung cancer. 14,30 These results point to the importance of this region for epithelium tumor development and allow to assume the existence of common mechanisms of gene down-regulation in this locus. Several groups of data indicate the existence of other epigenetic mechanisms, besides DNA methylation, inactivating these genes.…”

CTDSPL (CTD (Carboxy-Terminal Domain, RNA Polymerase II, Polypeptide A) Small Phosphatase-Like)

“…-Decrease in mRNA in ACs was due to deletion (25% cases) and promoter methylation (38% cases), whereas for SCCs, it was in 30% and 80% cases for deletion and methylation respectively (Senchenko et al, 2008). -Fold decrease in expression of RBSP3 in AC and SCC was 78% and 88% respectively, with overall 85% decrease in expression of RBSP3 in NSCLC (Senchenko et al, 2010). Oncogenesis Deletion and methylation of promoter of RBSP3 are responsible for reduction in expression of the protein and play important roles in progression of NSCLC (Senchenko et al, 2008).…”

“…Oncogenesis Deletion and methylation of promoter of RBSP3 are responsible for reduction in expression of the protein and play important roles in progression of NSCLC (Senchenko et al, 2008). Reduction of expression of RBSP3 is required for development of lung adenocarcinomas (Senchenko et al, 2010).…”