Re-expression of tumorigenicity after attenuation of human synaptotagmin 13 in a suppressed microcell hybrid cell line

Abstract

Abstract. Human chromosome 11p11.2 contains a putative liver tumor suppressor locus that was identified using a microcell hybrid cell line-based model of tumor suppression. Transcription mapping of suppressed microcell hybrid cell lines suggests that human SYT13 represents a strong candidate for the 11p11.2 tumor suppressor gene. Other evidence suggests that the putative 11p11.2 tumor suppressor gene (SYT13 or some other) may modulate the tumorigenic potential of neoplastic liver cell lines through direct or indirect regulation of the rat Wt1 tumor suppressor gene. To characterize a functional role for SYT13 in liver tumor suppression, we employed RNAi to attenuate SYT13 expression in a suppressed microcell hybrid cell line (GN6TF-11 neo CX4). SYT13-attenuated cells display aggressive phenotypic properties that are similar to or indistinguishable from the parental tumor cells (GN6TF), including altered cellular morphologies, disrupted contact inhibition, elevated saturation densities, restoration of anchorage-independent growth and increased tumorigenicity in vivo. Moreover, SYT13 attenuation and re-expression of tumorigenicity in GN6TF-11 neo CX4-derived cell lines was accompanied by a significant decrease of Wt1 expression. In contrast, the phenotypic properties of scrambled-control cells were similar to the suppressed microcell hybrid cells and Wt1 expression was unaffected. These observations combine to establish that: i) human SYT13 functions as a liver tumor suppressor gene that complements a molecular defect in GN6TF rat liver tumor cells resulting in a normalized cellular phenotype in vitro and suppression of tumorigenicity in vivo; ii) RNAi-mediated attenuation of SYT13 expression restores the neoplastic phenotype of GN6TF-11 neo CX4 microcell hybrid cells, consistent with the function of a liver tumor suppressor gene; and iii) loss of Wt1 expression is important for the re-establishment of tumorigenic potential by GN6TF-11 neo CX4 microcell hybrid cells after attenuation of SYT13. IntroductionHepatocellular carcinogenesis is a multi-step process that results from altered expression of multiple genes as a consequence of genetic mutations, epigenetic mechanisms, and/or chromosomal aberrations affecting a number of chromosome arms (1,2), including chromosome 11p (3-6).Comparative mapping studies suggest strongly that hepatocarcinogenesis in humans and rodents may be governed by orthologous tumor suppressor genes (7). We exploited this supposition to identify human liver tumor suppressor genes using a functional model for tumor suppression based on microcell-mediated transfer of human chromosome 11 into the aggressive rat liver tumor cell line GN6TF (8). The resulting microcell hybrid cell lines exhibit normalized cellular morphology, re-expression of contact inhibition, complete loss of anchorage-independent growth potential, and decreased tumorigenicity in vivo, suggesting that human chromosome 11 contains one or more liver tumor suppressor genes (8). Genomic mapping localized the liver tumor suppressor ...

A manual collection of Syt, Esyt, Rph3a, Rph3al, Doc2, and Dblc2 genes from 46 metazoan genomes - an open access resource for neuroscience and evolutionary biology

“…Transcript sequences from H. sapiens indicate the expression of a form lacking the TM domain. A recent study suggests that human SYT13 may function as a tumour supressor [ 83 ].…”

Synaptotagmin XIII expression and peritoneal metastasis in gastric cancer

“…The synaptotagmin family includes proteins that mediate membrane trafficking. Unlike other synaptotagmins, SYT13 lacks the extracellular N‐terminus and critical residues required for calcium binding. These distinctive characteristics, as well as its widespread distribution in brain, indicate that SYT13 is involved in constitutive vesicular transport, but little is known about its role in cancer.…”

Silencing of synaptotagmin 13 inhibits tumor growth through suppressing proliferation and promoting apoptosis of colorectal cancer cells

“…Grønborg et al reported reduced expression of SYT13 in a genome-wide analysis of pancreatic ductal adenocarcinoma compared with normal cells (17). Moreover, Jahn et al reported that human SYT13 acts as a liver tumor suppressor gene by complementing the molecular defect in GN6TF rat liver tumor cells to achieve normalized cellular phenotype and suppression of tumorigenicity (18).…”