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Background Vitamin D3 (VitD) deficiency is linked to increased incidence and worse survival in bladder cancer (BCa). In addition to cystectomy, patients are treated with cisplatin-based chemotherapy, however 30%-50% of patients do not benefit from this treatment. The effects of VitD deficiency on response to chemotherapy remain unknown. Methods To test effects of VitD supplementation on the response to cisplatin we analyzed patient serum VitD levels and correlated that with survival. In vivo, VitD deficient mice were treated with cisplatin, with or without pretreatment with the active VitD metabolite, 1,25 dihydroxyvitamin D3 (1,25D3 ). Lastly, using BCa cell lines, T24 and RT-112, the mechanism of action of 1,25D3 and cisplatin combination treatment was determined by apoptosis assays, as well as western blot and RT-PCR. Results In this study, we determined that low serum 25 hydroxyvitamin D3 (25D3 ) levels was significantly associated with worse response to cisplatin. Pretreating deficient mice with 1,25D3 , reduced tumor volume compared to cisplatin monotherapy. In vitro, 1,25D3 pretreatment increased the apoptotic response to cisplatin. 1,25D3 pretreatment increased expression of TAp73 and its pro-apoptotic targets, in a VDR dependent manner. VDR and its transcriptional targets were induced after 1,25D3 treatment and further increased after the combination of 1,25D3 and cisplatin in a TAp73 dependent manner. Conclusions Our data suggest that VitD deficiency could be a biomarker for poor response to cisplatin, and pretreating with VitD can increase the apoptotic response to cisplatin through VDR and TAp73 signaling crosstalk.

We observed a 53% response rate in non-small cell lung cancer (NSCLC) patients treated with vorinostat plus paclitaxel/carboplatin in a Phase I trial. Studies were undertaken to investigate the mechanism (s) underlying this activity. Growth inhibition was assessed in NSCLC cells by MTT assay after 72 hr of continuous drug exposure. Vorinostat (1 microM) inhibited growth by: 17% +/- 7% in A549, 28% +/- 6% in 128-88T, 39% +/- 8% in Calu1 and 41% +/- 7% in 201T cells. Vorinostat addition to carboplatin or paclitaxel led to significantly greater growth inhibition than chemotherapy alone in all 4 cell lines. Vorinostat (1 microM) synergistically increased the growth inhibitory effects of carboplatin/paclitaxel in 128-88T cells. When colony formation was measured after drug withdrawal, vorinostat significantly increased the effects of carboplatin but not paclitaxel. The % colony formation was control 100%; 1 microM vorinostat, 83% +/- 10%; 5 microM carboplatin, 41% +/- 11%; carboplatin/vorinostat, 8% +/- 4%; 2 nM paclitaxel, 53% +/- 11%; paclitaxel/vorinostat, 46% +/- 21%. In A549 and 128-88T, vorinostat potentiated carboplatin induction of gamma-H2AX (a DNA damage marker) and increased alpha-tubulin acetylation (a marker for stabilized mictrotubules). In A549, combination of vorinostat with paclitaxel resulted in a synergistic increase in alpha-tubulin acetylation, which reversed upon drug washout. We conclude that vorinostat interacts favorably with carboplatin and paclitaxel in NSCLC cells, which may explain the provocative response observed in our clinical trial. This likely involves a vorinostat-mediated irreversible increase in DNA damage in the case of carboplatin and a reversible increase in microtubule stability in the case of paclitaxel.

1Alpha,25-dihydroxyvitamin D3 (1,25D3) displays potent antiproliferative activity in a variety of tumor model systems and is currently under investigation in clinical trials in cancer. Studies were initiated to explore its potential in nonsmall cell lung cancer (NSCLC), as effective approaches to the treatment of that disease are needed. In evaluating factors that may affect activity in NSCLC, the authors found that CYP24 (25-hydroxyvitamin D3-24-hydroxylase), the enzyme that catabolizes 1,25D3, is frequently expressed in NSCLC cell lines but not in the nontumorigenic bronchial epithelial cell line, Beas2B. CYP24 expression by RT-PCR was also detected in 10/18 primary lung tumors but in only 1/11 normal lung tissue specimens. Tumor-specific CYP24 upregulation was confirmed at the protein level via immunoblot analysis of patient-matched normal lung tissue and lung tumor extracts. Enzymatically active CYP24 is expected to desensitize NSCLC cells to 1,25D3. The authors therefore implemented a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) assay for 1,25D3 and its CYP24-generated metabolites to determine whether NSCLC cells express active enzyme. Analysis of NSCLC cell cultures revealed time-dependent loss of 1,25D3 coincident with the appearance of CYP24-generated metabolites. MK-24(S)-S(O)(NH)-Ph-1, a specific inhibitor of CYP24, slowed the loss of 1,25D3 and increased 1,25D3 half-life. Furthermore, combination of 1,25D3 with MK-24(S)-S(O)(NH)-Ph-1 resulted in a significant decrease in the concentration of 1,25D3 required to achieve maximum growth inhibition in NSCLC cells. These data suggest that increased CYP24 expression in lung tumors restricts 1,25D3 activity and support the preclinical evaluation of CYP24 inhibitors for lung cancer treatment.

Recent data provides evidence for an important role of vitamin (Vit) D in respiratory muscle health. We tested the hypothesis that Vit D deficiency will reduce diaphragm muscle strength. Fifteen A/...