Chmp 1A is a mediator of the anti-proliferative effects of All-trans Retinoic Acid in human pancreatic cancer cells

Abstract

BackgroundWe recently have shown that Charged multivesicular protein/Chromatin modifying protein1A (Chmp1A) functions as a tumor suppressor in human pancreatic tumor cells. Pancreatic cancer has the worst prognosis of all cancers with a dismal 5-year survival rate. Preclinical studies using ATRA for treating human pancreatic cancer suggest this compound might be useful for treatment of pancreatic cancer patients. However, the molecular mechanism by which ATRA inhibits growth of pancreatic cancer cells is not clear. The objective of our study was to investigate whether Chmp1A is involved in ATRA-mediated growth inhibition of human pancreatic tumor cells.ResultsWe performed microarray studies using HEK 293T cells and discovered that Chmp1A positively regulated Cellular retinol-binding protein 1 (CRBP-1). CRBP-1 is a key regulator of All-trans retinoic acid (ATRA) through ATRA metabolism and nuclear localization. Since our microarray data indicates a potential involvement of Chmp1A in ATRA signaling, we tested this hypothesis by treating pancreatic tumor cells with ATRA in vitro. In the ATRA-responsive cell lines, ATRA significantly increased the protein expression of Chmp1A, CRBP-1, P53 and phospho-P53 at serine 15 and 37 position. We found that knockdown of Chmp1A via shRNA abolished the ATRA-mediated growth inhibition of PanC-1 cells. Also, Chmp1A silencing diminished the increase of Chmp1A, P53 and phospho-P53 protein expression induced by ATRA. In the ATRA non-responsive cells, ATRA did not have any effect on the protein level of Chmp1A and P53. Chmp1A over-expression, however, induced growth inhibition of ATRA non-responsive cells, which was accompanied by an increase of Chmp1A, P53 and phospho-P53. Interestingly, in ATRA responsive cells Chmp1A is localized to the nucleus, which became robust upon ATRA treatment. In the ATRA-non-responsive cells, Chmp1A was mainly translocated to the plasma membrane upon ATRA treatment.ConclusionCollectively our data provides evidence that Chmp1A mediates the growth inhibitory activity of ATRA in human pancreatic cancer cells via regulation of CRBP-1. Our results also suggest that nuclear localization of Chmp1A is important in mediating ATRA signaling.

The Roles of ESCRT Proteins in Healthy Cells and in Disease

“…In addition, Vps37A expression in hepatocellular carcinomas was found to be dramatically reduced or undetected suggesting that Vps37A may be a potential tumour suppressor (Xu et al, 2003). Similar results were observed with CHMP1A, as overexpression of this protein inhibited cell growth and tumour formation in human pancreatic tumor cells (Li et al, 2009).…”

“…The Roles of ESCRT Proteins in Healthy Cells and in Disease 467 al., 1998), Vps37A (Xu et al, 2003) and CHMP1A (Li et al, 2009) have been identified as potential tumor suppressors. However several other subsequent studies found Tsg101 to play a role in cell cycle control, a conclusion that is in contradiction to the tumor suppressor properties of Tsg101 (Zhu et al, 2004).…”

Chromatin modifying protein 1A (Chmp1A) of the endosomal sorting complex required for transport (ESCRT)-III family activates ataxia telangiectasia mutated (ATM) for PanC-1 cell growth inhibition

“…42,50 Since Chmp1A induces ATM activation, it is possible that the dense structures shown in Previously we have shown that Chmp1A was recruited to the nucleus upon ATRA treatment in ATRA-responsive pancreatic tumor cells. With the same treatment, however, Chmp1A was localized at the membrane in ATRA non-responsive cells, 41 demonstrating the significance of nuclear localization for the mediation of the ATRA signal. NLS-predicting PSORT program identified a bipartite NLS in Chmp1A and Hollenberg's lab also reported the presence of a NLS in Chmp1A protein.…”

“…Evidence of Chmp1A as a tumor suppressor includes: reduced/mis-localized expression of Chmp1A in various human pancreatic tumors relative to normal pancreatic tissue; decreased growth in cell culture and of xenograft tumors upon Chmp1A overexpression in human pancreatic ductal tumor (PanC-1) cells; accumulation of phospho-p53 (pP53) upon Chmp1A overexpression; and growth promotion of PanC-1 cells and conversion of non-tumorigenic human embryonic kidney cells to cells capable of forming xenograt tumors in athymic mice by stable knock-down of Chmp1A. 40 Furthermore, Chmp1A protein localizes to the nucleus in alltrans retinoic acid (ATRA)-responsive PanC-1 cells upon ATRA treatment, 41 demonstrating the significance of nuclear localization of Chmp1A in the mediation of ATRA signaling.…”

Inhibitory effect of cucurbitacin E on pancreatic cancer cells growth via STAT3 signaling

“…Compared with untreated patients, the median disease-free survival following complete resection of the cancer and adjuvant administration of gemcitabine has reached 13.4 months (as compared with 6.9 months for the former). However, in terms of overall survival, this longer disease-free survival has not achieved much advantage (Kullmann et al 2009;Li et al 2009). Therefore, studies are now focusing on evaluation of new agents for the treatment of metastatic pancreatic cancers (Brell et al 2009;Lee et al 2009;Saif et al 2009).…”