TSG101 is not mutated in lung cancer but a shortened transcript is frequently expressed in small cell lung cancer

Abstract

TSG101 is a candidate tumor suppressor gene whose deletion in NIH3T3 cells leads to spontaneous lung metastases in nude mice. Aberrant transcripts of TSG101 have been identi®ed in 47% of primary breast carcinomas, without evidence of intragenic deletions at the TSG101 locus on 11p15. To investigate the possible role of TSG101 in lung cancer, which often shows 11p allele loss, we performed transcript analysis and mutational analysis of TSG101 in lung cancer cell lines. Reverse transcriptase RT ± PCR and Northern analysis detected a common TSG101 transcript, shortened because of an internal deletion, which was expressed simultaneously with the wild-type transcript in 89% of small cell lung cancer (SCLC) lines. In contrast, the wild-type transcript was expressed alone in normal tissues, primary non-small cell lung cancer (NSCLC) specimens, and the majority of NSCLC cell lines. Sequence of the shortened SCLC transcript was identical to that of the most common aberrant transcript identi®ed in breast cancer, consisting of a deletion of exons 2 ± 4 and part of 1 and 5. Southern analysis of SCLC lines expressing the shortened transcript did not detect any intragenic deletions. Single strand conformational polymorphism (SSCP) analysis and direct sequencing of TSG101 cDNAs also identi®ed no mutations or deletions. These results suggest that TSG101 is not mutated in lung cancer but that aberrant splicing of TSG101 occurs in SCLC.

Altered patterns of expression of members of the heterogeneous nuclear ribonucleoprotein (hnRNP) family in lung cancer

“…The observed modifications in the expression of members of the hnRNP family in lung cancer is in agreement with the reported abnormalities in alternative splicing of cancer-related proteins such as BRCA1 [2], cyclin D1 [3], mdm2 [4], FHIT [5], TSG101 [6] or VEGF [7]. One of the best characterized example of a protein with distinct splicing forms in cancer is CD44.…”

Expression of a new isoform of the tumor susceptibility TSG101 protein lacking a leucine zipper domain in Burkitt lymphoma cell lines

“…Most of the TSG101 deletions detected in BL and resulting in non coding transcripts are similar to those reported in breast (Lee and Feinberg, 1997;Li et al, 1997;Steiner et al, 1997), prostate carcinomas (Sun et al, 1997), small cell lung carcinoma (Oh et al, 1998) and acute myeloid leukemia (Lin et al, 1998). These splicing aberrations can also be detected in normal cells although at a much lower frequency, suggesting there is a biological selection for them in tumor cells (Gayther et al, 1997;Oh et al, 1998). Among these, the joining of nucleotides 153 ± 1055 represents the most common and abundant aberrant transcript in all types of tumors breast (Lee and Feinberg, 1997;Li et al, 1997;Lin et al, 1998;Oh et al, 1998;Steiner et al, 1997;Sun et al, 1997).…”

“…These splicing aberrations can also be detected in normal cells although at a much lower frequency, suggesting there is a biological selection for them in tumor cells (Gayther et al, 1997;Oh et al, 1998). Among these, the joining of nucleotides 153 ± 1055 represents the most common and abundant aberrant transcript in all types of tumors breast (Lee and Feinberg, 1997;Li et al, 1997;Lin et al, 1998;Oh et al, 1998;Steiner et al, 1997;Sun et al, 1997). In this report we have identi®ed a splicing variant that can code for a truncated form of the TSG101 protein, lacking a leucine zipper dimerization domain, that can have biological implications and its presence is detected in 16 of 22 or 72% of the BL cell lines.…”

“…Aberrantly spliced TSG101 messages with loss of coding exons are frequently detected in breast (Lee and Feinberg, 1997;Steiner et al, 1997), prostate (Sun et al, 1997), small cell lung carcinomas (Oh et al, 1998) and acute myeloid leukemia (Lin et al, 1998). In some cases the aberrant messages might be the result of rearrangements at the DNA level (Lee and Feinberg, 1997;Steiner et al, 1997).…”

Stress-induced aberrant splicing of TSG101: association to high tumor grade and p53 status in breast cancers

“…Moreover, initial reports of truncated PCR products of genomic DNA suggested the presence of intragenic deletions of TSG101 gene in many spontaneous human breast cancers. However, later studies of direct Southern blot on breast tumor samples probed with TSG101 cDNA failed to demonstrate any genomic rearrangements, including some with truncated transcripts (Chang et al, 1999;Gayther et al, 1997;Lee and Feinberg, 1997;Oh et al, 1998;Steiner et al, 1997). Detailed analysis of these truncated transcripts demonstrates that they result from aberrant splicing on a limited number of cryptic splice acceptor/donor sites (Gayther et al, 1997;Lee and Feinberg, 1997;Wagner et al, 1998).…”