Regulation of Drug Sensitivity of Gastric Cancer Cells by Human Calcyclin-binding Protein (CacyBP)

Background: Calcyclin-binding protein (CacyBP) was previously identified as an upregulated gene in a multidrug-resistant gastric cancer cell line, SGC7901/ADR, compared to its parental cells, SGC7901, by subtractive hybridization. The aim of this study was to explore the role of CacyBP in multidrug resistance (MDR) in gastric cancer cells.

Methods: The cDNA encoding CacyBP was generated by reverse-transcription-polymerase chain reaction (RT-PCR), and mouse antisera against CacyBP was raised using recombinant CacyBP as the immunogen. The expression of CacyBP in gastric cancer cells was determined by Northern and Western blots. Sense and antisense vectors for CacyBP were introduced into SGC7901 and SGC7901/ADR cells, respectively. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was performed to evaluate the drug sensitivity of gastric cancer cells. Flow cytometry was employed to determine adriamycin accumulation and retention in gastric cancer cells.

Results: Northern and Western blots demonstrated upregulation of CacyBP in SGC7901/ADR cells compared to SGC7901 cells. SGC7901-CacyBP and SGC7901/ADR-anCacyBP cells were prepared, in which CacyBP was genetically increased and decreased, respectively. As compared with SGC7901, SGC7901-CacyBP cells exhibited significantly increased ( P < 0.01) IC(50) values for vincristine, adriamycin, and 5-fluorouracil. Meanwhile, as compared with SGC7901/ADR, SGC7901/ADR-anCacyBP cells exhibited significantly decreased ( P < 0.01) IC(50) values for these three drugs. SGC7901-CacyBP and SGC7901/ADR-anCacyBP cells displayed no obvious difference ( P > 0.05) in intracellular adriamycin content compared to their corresponding parental cells.

Conclusions: Upregulation of CacyBP is associated with MDR in gastric cancer cells. CacyBP could regulate the responses of gastric cancer cells to chemotherapy. But the underlying mechanisms of CacyBP-related MDR need further identification.