Flavonoids and cancer prevention: a review of the evidence. and increased its accumulation in the cells, but Methylnaltrexone Bromide did not add to the transport inhibitory effect of anti-Rlip antibodies alone. Binding of Rlip to 2HF was evident from successful purification of Rlip by 2HF affinity chromatography. Consistent with increased drug accumulation, combined treatment with 1-chloro-2, 4-dinitrobenzene, reduced the GI50 of 2HF by an order of magnitude. Results of nude mouse xenograft studies of SCLC and NSCLC, which showed that orally administered 2HF inhibited growth of both histological types of lung cancer, confirmed study results. Our result suggest that Rlip inhibition is likely a mechanism of action. Our findings are basis of proposing 2HF as therapeutic or preventative drug for lung cancer. gene) is a high-capacity ATP-dependent transporter responsible for the bulk of GS-E removal. An existential necessity of Rlip for survival of cancer cells is suggested by studies showing that Rlip deficiency strongly prevents benzo[a] pyrene induced carcinogenesis [17]. The magnitude of this cancer preventative effect was evident in recently reported studies showing that Rlip haploinsufficiency is sufficient to prevent spontaneous carcinogenesis in null mice [28]. Depleting Rlip by antisense or siRNA, or inhibition by anti-Rlip antibodies causes regression, not simply a growth delay, of syngeneic melanoma, and allogeneic xenografts of human neuroblastoma, and lung as well as kidney, prostate, pancreas, and colon cancer [29]. Thus, Rlip targeting should also have a therapeutic role in established malignancy. We studied the effects of 2HF in lung cancer cell lines and found that 2HF displays strong anticancer activity in Rabbit Polyclonal to GABRA6 both small cell and non-small cell histologies of lung cancer associated and present evidence of direct interaction of 2HF with Rlip. RESULTS Rlip is expressed human lung cancer The expression of the Rlip analyzed showed remarkable differences amongst the human Methylnaltrexone Bromide adenocarcinoma of lung tissue sections and adjacent normal tissue. Using immunohistochemistry (IHC), tissues affected with adenocarcinoma showed significantly strong Rlip expression (Figure ?(Figure1A)1A) in cancerous tissues. On the contrary, adjacent normal tissue showed basal Rlip expression. Quantification of Rlip expression (Figure ?(Figure1B)1B) in tissues using image pro, reveals a significant difference (= 0.0386) in staining intensity of Rlip between cancerous tissue and the adjacent normal tissue. Thus, higher Rlip expression may be responsible for drug resistance in lung cancer patients. Open in a separate window Figure 1 Immunohistochemistry analysis of Rlip protein expression in human adenocarcinoma of lung tissue sectionsUnidentified lung cancer and adjacent normal lung tissue were analyzed by IHC using anti-Rlip antibodies and representative photomicrographs are shown (A). IHC quantification of Rlip expression in tissues was performed using image pro (B) (= 8). 2HF inhibited growth and survival of lung cancer cell lines Concentration dependent growth inhibitory effects of 2HF was also observed in the wild-type squamous cell histology H520 and H358 NSCLC cell line, and well as in the mutant H1417 and H1618 SCLC cell lines. The two SCLC cell lines were somewhat more sensitive to 2HF (average GI50 21 M) than the NSCLC cell lines (average GI50 52 M, 0.01) (Figure ?(Figure2A).2A). Clonogenic assays confirmed that 2HF inhibited lung cancer cell survival as shown for the H358 and H520 NSCLC cell lines (54 and 46% inhibition, respectively, 0.001). The immortalized non-malignant human lung bronchioepithelial cell line HLBEC grew significantly slower than the malignant cell lines as expected and its survival was not significantly affected by 2HF in clonogenic assays (Figure ?(Figure2B).2B). The GI50 of 2HF towards these lung cancer cell lines ranged from 20 to 80 M, in a concentration range observed for many generally regarded as safe natural compounds that are sufficiently non-toxic to achieve these concentrations upon oral dosing, even in humans [23]. Importantly, 2HF Methylnaltrexone Bromide inhibited the growth of ALK (anaplastic lymphoma kinase) gene-rearranged H3122 and H2228 adenocarcinoma NSCLC cell lines. This is significant because ALK rearranged adenocarcinomas are resistant to the commonly used EGFR kinase inhibitors. Furthermore, the H2228 cell line displays acquired resistance to ALK-inhibition, GI50 of 2HF being 84 5 62 5 M for H2228 and H3122, respectively ( 0.01) (Figure ?(Figure2C2C). Open in a separate window Figure 2 Anticancer activity of 2-hydroxyflavonone and effect of Rlip expression in lung cancer cell linesWe examined the differential toxicity of 2HF in non-malignant human lung bronchioepithelial cells (HLBEC) compared with the H1417 and H1618 SCLC and the H358 and H520 NSCLC cell lines (A). The cytotoxicity of 2HF on the H358 and H520 NSCLC cell lines was further confirmed by a colony-forming assay is shown (B). The growth inhibitory activity of 2HF toward ALK-rearrangement harboring H3122 and H2228 cell line (C). The growth inhibitory effect of polyclonal rabbit-anti-human anti-Rlip IgG.