Higher potency of N-(4-hydroxyphenyl)retinamide than all-trans-retinoic acid in induction of apoptosis in non-small cell lung cancer cell lines.

Most human non-small cell lung cancer (NSCLC) cell lines are refractory to all-trans-retinoic acid (ATRA). Recently, N-(4-hydroxyphenyl)retinamide (4HPR) was found to induce apoptosis in various tumor cells. In this study, we compared and contrasted the effects of 4HPR and ATRA on the growth and apoptosis of 10 NSCLC cell lines and normal human bronchial epithelial (NHBE) cells. All of the cancer cell lines and the NHBE cells were sensitive to 10 microM 4HPR, and their numbers decreased to <20% of the controls after a 5-day treatment, whereas ATRA decreased cell numbers to about 50% of the controls in three cell lines and was less effective in the rest of the tumor cell lines. ATRA inhibited the growth of the NHBE cells by 70-80%. 4HPR induced apoptosis in most of the cells, including the ATRA-resistant ones, as evidenced by a DNA fragmentation assay. No correlation was found between growth inhibition by 4HPR and the expression of retinoic acid receptor beta (determined by Northern blotting and PCR), p53, or Bcl-2 proteins (analyzed by Western blotting). These results demonstrate that 4HPR is more potent than ATRA in inducing apoptosis in NSCLC cells and suggest that further clinical trials for prevention and therapy of NSCLC using 4HPR are warranted.