Clinical validation study of genetic markers for capecitabine efficacy in metastatic colorectal cancer patients.

BACKGROUND AND AIM: Pharmacogenetic studies continue to search for pretreatment predictors of chemotherapeutic efficacy and toxicity in metastatic colorectal cancer. Both genome-wide association studies and candidate gene studies have yielded potential genetic markers for chemosensitivity. We conducted a clinical association study, validating the effect of specific genetic markers cited in recently published papers on the efficacy of the oral 5-fluoro-uracil prodrug capecitabine. PATIENTS AND METHODS: Germline DNA was collected for 268 metastatic colorectal cancer patients from the CAIRO trial, a multicenter phase III trial, randomizing between combined or sequential first-line treatment with capecitabine, irinotecan, and oxaliplatin. Genotyping was performed for eight single-nucleotide polymorphisms (SNPs), using high-resolution melting curves. Four SNPs are located in the MTRR gene, and another four SNPs showed significant association with 5-fluoro-uracil cytotoxicity in a recent in-vitro genome-wide association study. The primary endpoint was progression-free survival (PFS); secondary endpoints were objective response and overall survival. RESULTS: In patients receiving capecitabine monotherapy, rs4702484, located in ADCY2 and close to MTRR, was associated with slightly reduced PFS for homozygous wild-type patients (CC 6.2 vs. CT 8.0 months; P=0.018). For the other selected genetic markers, we found no association with PFS, overall survival, or radiologic response upon treatment with capecitabine, either in the total study population or in the capecitabine monotherapy subgroup. CONCLUSION: With the exception of rs4702484, we found no evidence of an effect on capecitabine chemosensitivity for any of the studied SNPs. More specifically, variants in methionine synthase reductase (MTRR) are not likely associated with capecitabine efficacy.

Brostallicin versus doxorubicin as first-line chemotherapy in patients with advanced or metastatic soft tissue sarcoma: an European Organisation for Research and Treatment of Cancer Soft Tissue and Bone Sarcoma Group randomised phase II and pharmacogenetic study.

AIM: Brostallicin is a DNA minor groove binder that has shown activity in patients with soft tissue sarcoma (STS) failing first-line therapy. The present study assessed the safety and efficacy of first-line brostallicin in patients with advanced or metastatic STS >60 years or not fit enough to receive combination chemotherapy. A prospective explorative pharmacogenetic analysis was undertaken in parallel. METHODS: Patients were randomised in a 2:1 ratio between IV brostallicin 10mg/m(2) and doxorubicin 75 mg/m(2) once every 3 weeks for a maximum of six cycles. Disease stabilisation at 26 weeks (primary end-point) was considered a 'success'. Further testing of brostallicin was warranted if ≥ 35 'successes' were observed in the first 72 eligible patients treated with brostallicin. In addition, patients were genotyped for glutathione S transferase (GST) polymorphisms. RESULTS: One hundred and eighteen patients were included (79 brostallicin and 39 doxorubicin). Brostallicin was well tolerated in comparison to doxorubicin with less grade 3-4 neutropenia (67% versus 95%), grade 2-3 systolic dysfunction (0% versus 11%), alopecia (17% versus 61%) and grade 2-3 mucositis (0% versus 18%). For brostallicin versus doxorubicin, 'successes' were observed in 5/77 versus 10/36, progression free survival at 1 year was 6.5% versus 15.6%, objective response rate was 3.9% versus 22.2% and overall survival at 1 year was 50.5% versus 57.9%, respectively. Only GSTA1 genotype was significantly associated with success rate of doxorubicin treatment. CONCLUSION: Brostallicin cannot be recommended at this dose and schedule in this patient population as first-line therapy. GSTA1 genotype may be predictive for doxorubicin efficacy but warrants further study.

Comparative toxicity of arsenite metabolites in wild type CHO cells and in cells deficient in excision repair cross-complementing 1 and 2.

Arsenic (As) has been shown to alter one or more DNA repair processes. Excision repair cross-complementing 1 and 2 (ERCC1 and ERCC2) have shown to be associated with arsenic-induced toxicity and carcinogenicity. In this study, we investigated cytotoxic effects of various As metabolites in relation to two nucleotide excision repair genes: ERCC1 and ERCC2. Various arsenate (pentavalent) and arsenite (trivalent) metabolites were tested in ERCC1, ERCC2 deficient and wild type cells. Our results showed that in the selected concentration range pentavalent As metabolites; iAs(V), MMA(V) and DMA(V) were not cytotoxic, unlike the trivalent As metabolites; iAs(III), MMA(III) and DMA(III). The measured LC(50) demonstrated a significant difference (p<0.01) for iAs(III) between the three cell lines, while MMA(III) and DMA(III) are more cytotoxic to all three cell lines. UV5 (ERCC2 deficient) cells also showed a lower resistance to iAs(III) in comparison to AA8 (wild type) and UV20 (ERCC2 deficient) cells. This might be explained through the generation of hydrogen peroxide (H(2)O(2)), which is generated by increase of intracellular Ca(2+) level. Generation of H(2)O(2) in UV5 cells after incubation with iAs(III) is significantly higher than AA8 and UV20 cells (p<0.01). In conclusion, absence of ERCC2 leads to a increased generation of H(2)O(2) by iAs(III) in UV5 cells, which is in contrast to AA8 and UV20 cells.

Mechanism of arsenic-induced neurotoxicity may be explained through cleavage of p35 to p25 by calpain.

In recent studies we have demonstrated that arsenic (As) metabolites change the composition of neuronal cytoskeletal proteins in vivo and in vitro. To further examine the mechanism of arsenic-induced neurotoxicity with various arsenate metabolites (iAsV, MMAV and DMAV) and arsenite metabolites (iAsIII, MMAIII and DMAIII), we investigated the role of the proteolytic enzyme calpain and its involvement in the cleavage of p35 protein to p25, and also mRNA expression levels of calpain, cyclin-dependent kinase 5 (cdk5) and glycogen synthase kinase 3 beta (gsk3ss). A HeLa cell line transfected with a p35 construct (HeLa-p35) was used as a model, since all other proteins such as calpain, CDK5 and GSK3beta are already present in HeLa cells as they are in neuronal cells. HeLa-p35 cells were incubated with various As metabolites and concentrations of 0, 10 and 30 microM for duration of 4 h. Subsequently the cells were either lysed to study their relative quantification levels of these genes or to be examined on their p35-protein expression. P35-RNA expression levels were significantly (p<0.01) increased by arsenite metabolites, while p35 protein was cleaved to p25 (and p10) after incubation with these metabolites. The cleavage of p35 is caused by calcium (Ca2+) induced activation of calpain. Inhibition of calpain activity by calpeptin prevents cleavage of p35 to p25. These results suggest that cleavage of p35 to p25 by calpain, probably As-induced Ca2+-influx, may explain the mechanism by which arsenic induces its neurotoxic effects.

Arsenic metabolites affect expression of the neurofilament and tau genes: an in-vitro study into the mechanism of arsenic neurotoxicity.

Neurological studies indicate that the central (CNS) and peripheral nervous system (PNS) may be affected by arsenic (As). As-exposed patients show significantly lower nerve conduction velocities (NCVs) in their peripheral nerves in comparison to healthy subjects. As may play a role in the disruption of neuroskeletal integrity, but the mechanisms by which it exerts a toxic effect on the peripheral and central nervous system are still unclear. In the present study, we examined the neurotoxic effects of various arsenic metabolites (iAs(III), iAs(V), MMA(V) and DMA(V)) on two different cell lines derived from the peripheral (ST-8814) and central (SK-N-SH) nervous system. The effects of the arsenic metabolites were examined on the relative quantification levels of the cytoskeletal genes, neurofilament-light (NEFL), neurofilament-medium (NEF3), neurofilament-heavy (NEFH) and microtubule-associated protein-tau (MAPT), using real-time PCR. Our results show that iAs(III) and iAs(V) have no significant effects on either cell lines. On the other hand, MMA(V) and DMA(V) cause significant changes in expression levels of NEF3 and NEFL genes, while the expression level of the NEFH gene is significantly increased in both cell lines.