title: CNT1 expression influences proliferation and chemosensitivity in drug-resistant pancreatic cancer cells.
abstract: Overcoming the inherent chemoresistance of pancreatic cancers remains a major goal of therapeutic investigations in this disease. In this study, we discovered a role for the human concentrative nucleoside transporter-1 (hCNT1; SLC28A1), a high-affinity pyrimidine nucleoside transporter, in determining the chemosensitivity of human pancreatic cancer cells to gemcitabine, the drug used presently as a standard of care. Compared with normal pancreas and pancreatic ductal epithelial cells, hCNT1 expression was frequently reduced in pancreatic tumors and tumor cell lines. In addition, hCNT1-mediated (3)H-gemcitabine transport was lower in pancreatic cancer cell lines and correlated with cytotoxic IC(50) estimations of gemcitabine. In contrast to gemcitabine-sensitive pancreatic cancer cell lines, MIA PaCa-2, a gemcitabine-resistant pancreatic cancer cell line, exhibited relatively restrictive, cell cycle-dependent hCNT1 expression and transport. hCNT1 translation was suppressed in the late G1-enriched MIA PaCa-2 cell population possibly in an miRNA-dependent manner, which corresponded with the lowest hCNT1-mediated gemcitabine transport during this phase. Although hCNT1 protein was induced during G1/S transition, increased hCNT1 trafficking resulted in maximal cell surface recruitment and transport-overshoot in the G2/M phase-enriched cell population. hCNT1 protein was directed predominantly to proteasomal or lysosomal degradation in S or G2/M phase MIA PaCa-2 cells, respectively. Pharmacological inhibition of hCNT1 degradation moderately increased cell surface hCNT1 expression and cellular gemcitabine transport in MIA PaCa-2 cells. Constitutive hCNT1 expression reduced clonogenic survival of MIA PaCa-2 cells and steeply augmented gemcitabine transport and chemosensitization. In addition to supporting a putative tumor suppressor role for hCNT1, our findings identify hCNT1 as a potential candidate to render drug-resistant pancreatic cancer cells amenable to chemotherapy.
authors.affiliation: Department of Phamaceutical and Biomedical Sciences, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: Yangzom D
authors.initials: YD
authors.lastname: Bhutia
authors.forename: Sau Wai
authors.initials: SW
authors.lastname: Hung
authors.forename: Bhavi
authors.initials: B
authors.lastname: Patel
authors.forename: Dylan
authors.initials: D
authors.lastname: Lovin
authors.forename: Rajgopal
authors.initials: R
authors.lastname: Govindarajan
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D026901:Membrane Transport Proteins; C065171:cif nucleoside transporter