Aberrant Splicing of the TSG101 Tumor Suppressor Gene in Human Breast and Ovarian Cancers

Objective: To determine whether large deletions or other alterations in the putative tumor suppressor gene TSG101 play a role in the molecular pathogenesis of breast and ovarian cancers.

Methods: Expression of TSG101 transcripts was examined in breast and ovarian cancers using the reverse transcriptase-polymerase chain reaction (RT-PCR), and selected transcripts were sequenced. Southern blot analysis was performed to determine whether there were genomic deletions in the TSG101 gene, and Northern blot analysis was used to examine the relative abundance of various transcripts.

Results: All the cancerous and normal breast tissue examined expressed full length 1145 base pair (bp) TSG101 transcripts. Additional truncated transcripts were seen using the RT-PCR in 57 (64%) of 89 primary breast cancers, 1 (20%) of 5 breast cancer cell lines, 3 (50%) of 6 normal breast tissues, 16 (64%) of 25 primary ovarian cancers and 1 (33%) of 3 ovarian cancer cell lines. Only the primary breast (21%) and ovarian (24%) cancers had three or more truncated transcripts. None of the normal tissues or cell lines examined had more than two aberrant transcripts. DNA sequencing revealed that the most commonly expressed truncated transcript arises because of loss of 902 bp between codons 153 and 1055. Only full length TSG101 transcripts were seen on Northern blot analysis of breast cancer cell lines, however. There was no evidence of genomic deletions in the TSG101 gene on Southern blot analysis.

Conclusion: Truncated TSG101 transcripts that probably represent splice variants are present in some breast and ovarian cancers, but there is no evidence to suggest that loss of this putative tumor suppressor gene plays a role in the molecular pathogenesis of these cancers.