Retinoic acid receptor gamma1 expression determines retinoid sensitivity in pancreatic carcinoma cells.

BACKGROUND & AIMS: Retinoids inhibit growth and induce differentiation in a variety of pancreatic carcinoma cells. The goal of this study was to examine the molecular mechanisms responsible for retinoid sensitivity.

METHODS

Anchorage-independent growth was examined in AR42J, DSL-6A/C1, and Capan-2 cells using a human tumor clonogenic assay. Retinoid receptors were characterized by a reverse-transcription polymerase chain reaction. Retinoic acid receptor gamma1 (RARgamma1) was stably transfected into AR42J cells using lipofectamin and into DSL-6A/C1 using ballistomagnetic gene transfer. Receptor expression was verified using Southern and Northern blotting as well as electrophoretic mobility shift assays.

RESULTS

Retinoid treatment resulted in a dose-dependent growth inhibition of Capan-2 cells, whereas growth was not affected in AR42J and DSL-6A/C1 cells. A selective loss of RARgamma1 expression was observed in both retinoid-resistant cell lines, whereas all other retinoid receptor subtypes showed an identical expression pattern. Retinoid treatment of three independent RARgamma1-expressing cell clones of AR42J and DSL-6A/C1 cells resulted in pronounced growth inhibition compared with wild-type control cells.

CONCLUSIONS

RARgamma1 expression determines sensitivity of pancreatic carcinoma cells to retinoid-mediated growth inhibition and might therefore serve as a valuable predictive marker for retinoid treatment of pancreatic cancer.