Capecitabine with/without mitomycin C: results of a randomized phase II trial of second-line therapy in advanced biliary tract adenocarcinoma

PURPOSE

Advanced biliary tract adenocarcinoma (BTA) is a rare tumor with a poor prognosis. Since no standard salvage chemotherapy regimen exists, we explored the activity of capecitabine alone or combined with mitomycin C.

METHODS

Patients aged 18-75 years and with KPS >50, with pathological diagnosis of BTA stratified based on site and stage of disease, were randomized to receive capecitabine 2000 mg/m(2) day 1-14 alone (ARM A) or in combination with mitomycin C 6 mg/m(2) day 1 (ARM B) as second-line therapy. Cycles were repeated in both arms every 3 weeks. Tumor assessment was performed every 2 months. The primary endpoint was the probability of being progression free at 6 months (PFS-6) from treatment start. According to the Fleming design, the study aimed to enroll 26 pts per arm. An exploratory endpoint was to assess thymidylate synthase (TS) and thymidine phosphorylase (TP) expression, as biomarkers predictive for clinical outcomes of capecitabine treatment.

RESULTS

Between October 2011 and 2013, 57 metastatic pts were enrolled: ARM A/B 28/29. Accordingly, 55 (26/29) pts were assessable for the primary endpoint: 2 (8%) ARM A and 3 (10%) ARM B pts were PFS-6. Main G3-4 toxicities were: hand-foot syndrome and transaminitis in 4/0%, and thrombocytopenia, diarrhea and fatigue in 0/3% of pts. No statistically significant correlation was found between TS or TP expression and pts' outcome.

CONCLUSIONS

Since capecitabine yielded a disappointing outcome and the addition of mitomycin C did not improve the results, new therapeutic strategies need to be explored to improve survival in this disease setting.

Comparative effects of rifabutin and rifampicin on cytochromes P450 and UDP-glucuronosyl-transferases expression in fresh and cryopreserved human hepatocytes

The aim of this study was to evaluate rifabutin (RBT) and rifampicin (RIF) capabilities in inducing various xenobiotic metabolizing enzymes such as cytochromes P450 (CYPs) and UDP-glucuronosyl-transferases (UGTs) in cultured fresh and cryopreserved human hepatocytes. Enzyme induction was assessed through the use of several diagnostic markers, i.e. testosterone, midazolam (MDZ), diazepam (DZP) and 7-ethoxyresorufin for CYP-dependent enzyme reactions; and AZT for UGT-dependent enzyme reactions. RBT concentrations (0.118, 0.708 microM) were selected according to previously published pharmacokinetic data in patients. The known CYP3A4 inducer in humans, RIF, was used as a positive control. At the concentrations used, no sign of cytotoxicity was evidenced. Both compounds were able to dose-dependently induce the overall metabolism of testosterone (approximately 2-fold for RBT, 4-fold for RIF) and the formation of the 6beta-hydroxylated-derivative (up to approximately 4-fold over control for RBT and approximately 10-fold for RIF), which is CYP3A4 dependent. The other hydroxylated metabolites (16alpha-OH and 2alpha-OH) were also enhanced. The metabolism of MDZ, which is specifically metabolized by CYP3A4 in humans, was also investigated following drug's exposure to hepatocytes. DZP one, which is governed by various CYPs, including CYP3A, was also investigated. RBT was shown to increase the biotransformation of both benzodiazepines (approximately 1.9-fold over control). Moreover, the effects of both drugs on ethoxyresorufin O-deethylase activity (EROD), which is representative of CYPIA1/2 isoforms, were tested. Results showed only a moderate induction of this marker (approximately 2-fold over control) when compared to the high effect observed after hepatocyte exposure to 3-methylcholantene (approximately 14-fold over control). Finally, the action of RBT and RIF on UGTs expression was investigated by using AZT as diagnostic substrate: glucuronides formation was not significantly affected by the two rifamycin derivatives. On the whole, exposure of fresh or cryopreserved human hepatocytes to RBT dose-dependently affected the levels of drug metabolizing enzymes in a dose-dependent manner. However, as already demonstrated by in vivo pharmacokinetic studies, its inducing properties towards CYPs, CYP3A in particular, are less pronounced than RIF.

Activation of the JAK/STAT pathway leads to proliferation of ST14A central nervous system progenitor cells

We were interested in whether central nervous system progenitor cells possess the signal transduction machinery necessary to mediate cytokine functions and whether this machinery can become activated upon stable expression of a particular cytokine receptor. For this purpose we utilized a previously obtained conditionally immortalized striatum-derived nestin-positive cell line (ST14A). We found that ST14A cells express Jak2, but not Jak1 or Tyk2. An identical pattern of expression was found in embryonic striatal tissue. To evaluate the susceptibility of these cytokine specific cytoplasmic transducers to activation, ST14A cells were stably transfected with the alpha and beta (AIC2A) chains of the murine interleukin-3 receptor. Four independent lines expressing both the alpha and beta receptor subunits were obtained. We found that cells from each of these lines were induced to proliferate upon exposure to interleukin-3. Dose response curve, antibody blocking experiments and binding studies revealed that the response was mediated by the reconstituted high affinity interleukin-3 receptor. Immunoprecipitation studies on these cells showed that Jak2 and Stat5 were being phosphorylated after stimulation of the reconstituted receptor. These results indicate that members of the JAK/STAT family of proteins are expressed in central nervous system progenitor cells and are susceptible to activation through stimulation of an exogenously expressed cytokine receptor, ultimately leading to cell proliferation.

Selective in vitro blockade of neuroepithelial cells proliferation by methylazoxymethanol, a molecule capable of inducing long lasting functional impairments

In order to characterize the antiproliferative effect of methylazoxymethanol neuroepithelial cells derived from the rat striata primordia at embryonic day 14 have been exposed to graded doses of this compound. It was found that methylazoxymethanol application to striatal neuroblasts elicits a blockade of cell proliferation at a dose which does not interfere with cell survival. By using synchronized cells and short term exposures to this compound, we found that the antiproliferative effect of methylazoxymethanol is strikingly correlated to the number of cells actively dividing in culture, thus indicating that the cells targeted by methylazoxymethanol must be in an active mitotic phase. To test for the selectivity of action of Methylazoxymethanol for dividing neuroblasts either cultures composed of mature proliferating astrocytes or muscle cells have been subjected to the same treatment. It has been observed that astrocytes proliferation was not affected by the dose of methylazoxymethanol shown to be effective on neuroepithelial cells. Finally we demonstrated that methylazoxymethanol is able only transiently to interfere with smooth muscle cell division, further supporting its selectivity of action within the developing CNS.