Chmp1A functions as a novel tumor suppressor gene in human embryonic kidney and ductal pancreatic tumor cells.

Chmp1A (Chromatin modifying protein 1A/Charged multivesicular protein 1A) is a member of the ESCRT-III (Endosomal Sorting Complex Required for Transport) family that was shown to function in endosome-mediated trafficking via multivesicular body (MVB) formation and sorting. Recent reports suggest that ESCRT complexes are also involved in cell cycle progression and tumor development. Using in vitro and in vivo model systems, we provide evidence that Chmp1A is a novel tumor suppressor, especially in the pancreas. We demonstrated that short hairpin RNA (shRNA) mediated stable silencing of Chmp1A in HEK 293T cells resulted in an increase of anchorage-independent growth in soft agar assay and tumor formation in xenograft assay. To investigate the involvement of Chmp1A in human tumor development we screened human cancer arrays and pancreatic tissue arrays. We discovered that Chmp1A mRNA and protein was reduced and/or altered (protein) in various human pancreatic tumors. To investigate the biological implication of these data, we either overexpressed or silenced Chmp1A in human pancreatic ductal tumor cells (PanC-1) and studied the effect of these manipulations on cell and tumor growth respectively. Stable overexpression of Chmp1A in PanC-1 cells resulted in cell growth inhibition and tumor xenograft inhibition respectively. In contrast, silencing of Chmp1A in PanC-1 cells resulted in the elevation of cell growth in vitro. Mechanistically, overexpression of Chmp1A strongly increased the protein level of p53 and phospho-P53. Taken together, our data indicates that Chmp1A is a novel tumor suppressor, especially in pancreas and that Chmp1A regulates tumor growth potentially through p53 signaling pathway.