Our previous studies utilized a microcell hybrid (MCH) cell line-based functional model of tumor suppression to localize a liver tumor suppressor to human chromosome 11, map the suppressor locus to a <1-Mb region within human 11p11.2, and identify a number of expressed sequence tags (ESTs) and genes that represent candidate liver tumor suppressor genes. The Human Genome Project has recently positioned a number of additional genes, ESTs, and predicted genes within the human 11p11.2 liver tumor suppressor region. In this study, we analyzed 26 ESTs and genes (known and predicted) that have been localized to human 11p11.2. Four of these ESTs/genes (FLJ23598, FLJ10450, KIAA1580, SYT13) mapped to the minimal tumor suppressor region of human 11p11.2, the smallest region conferring suppression of tumorigenicity in the MCH cell lines. Each of these ESTs/genes were expressed among an index panel of suppressed MCH cell lines (derived from GN6TF rat liver tumor cells), suggesting that these ESTs/genes represent excellent candidates for the human 11p11.2 liver tumor suppressor gene. To verify the candidate status of these sequences, 8 additional MCH cell lines (derived from GN3TG and GP10TA rat liver tumor cells) were analyzed. Three ESTs/genes (FLJ23598, FLJ10450, KIAA1580) proved to be less than ideal candidates, based upon their loss from suppressed MCH cell lines (DNA deletion), and/or their retention and expression in a non-suppressed MCH cell line. In contrast, SYT13 is present in the DNA from all suppressed MCH cell lines (n=10), and is deleted in a non-suppressed MCH cell line. Furthermore, SYT13 mRNA is expressed in 100% of suppressed cell lines, and is not expressed in the non-suppressed MCH cell line or in MCH-derived tumor cell lines (n=6). These results suggest that SYT13 is an excellent candidate for the human 11p11.2 liver tumor suppressor gene based upon its: i) location within the human 11p11.2 liver tumor suppressor region; ii) loss from the DNA of a non-suppressed MCH cell line that lacks the human 11p11.2 liver tumor suppressor region; iii) expression among suppressed MCH cell lines; and iv) lack of expression by MCH-derived tumor cell lines.

Related Articles