Suppressor of tumorigenicity 20 protein
cysteine-type endopeptidase activator activity
Candidate tumor suppressor, HCCS-1, is downregulated in human cancers and induces apoptosis in cervical cancer.
To identify the genes involved in cervical carcinogenesis, we applied the mRNA differential display method and identified a candidate tumor suppressor gene, HCCS-1, which was present in normal cervical tissue but absent in cervical cancer, metastatic lymph node and CUMC-6 cervical cancer cell line. HCCS-1 transcripts were expressed in many normal tissues including leukocyte, lung, spleen, liver, heart and uterine cervix. Its expression was absent in 8 human cancer cell lines. HCCS-1-transfected HeLa cells exhibited growth inhibition by about 50%. This inhibitory effect of HCCS-1 on cervical cancer cells was associated with apoptotic process including DNA fragmentation. HCCS-1-transfected HeLa cells were shown to release cytochrome c from mitochondria, which activates caspase-9 and -3 and finally results in cleavage of poly(ADP-ribose) polymerase. Apoptosis formation was detected by propidium-iodide/annexin V. HCCS-1-transfected HeLa cells were more sensitive to adriamycin or UVC ray triggered apoptosis. These results suggest that HCCS-1 is downregulated in multiple human tumor types and may serve as a candidate tumor suppressor gene through apoptotic pathway against human cervical cancer.