Bevin C. English

Hypertension and hand-foot skin reactions related to VEGFR2 genotype and improved clinical outcome following bevacizumab and sorafenib

BackgroundHypertension (HT) and hand-foot skin reactions (HFSR) may be related to the activity of bevacizumab and sorafenib. We hypothesized that these toxicities would correspond to favorable outcome in these drugs, that HT and HFSR would coincide, and that VEGFR2 genotypic variation would be related to toxicity and clinical outcomes.MethodsToxicities (≥ grade 2 HT or HFSR), progression-free survival (PFS), and overall survival (OS) following treatment initiation were evaluated. Toxicity incidence and VEGFR2 H472Q and V297I status were compared to clinical outcomes.ResultsIndividuals experiencing HT had longer PFS following bevacizumab therapy than those without this toxicity in trials utilizing bevacizumab in patients with prostate cancer (31.5 vs 14.9 months, n = 60, P = 0.0009), and bevacizumab and sorafenib in patients with solid tumors (11.9 vs. 3.7 months, n = 27, P = 0.052). HT was also linked to a > 5-fold OS benefit after sorafenib and bevacizumab cotherapy (5.7 versus 29.0 months, P = 0.0068). HFSR was a marker for prolonged PFS during sorafenib therapy (6.1 versus 3.7 months respectively, n = 113, P = 0.0003). HT was a risk factor for HFSR in patients treated with bevacizumab and/or sorafenib (OR(95%CI) = 3.2(1.5-6.8), P = 0.0024). Carriers of variant alleles at VEGFR2 H472Q experienced greater risk of developing HT (OR(95%CI) = 2.3(1.2 - 4.6), n = 170, P = 0.0154) and HFSR (OR(95%CI) = 2.7(1.3 - 5.6), n = 170, P = 0.0136).ConclusionsThis study suggests that HT and HFSR may be markers for favorable clinical outcome, HT development may be a marker for HFSR, and VEGFR2 alleles may be related to the development of toxicities during therapy with bevacizumab and/or sorafenib.

Sorafenib is an Inhibitor of UGT1A1 but is Metabolized by UGT1A9: Implications of Genetic Variants on Pharmacokinetics and Hyperbilirubinemia

Purpose: Several case reports suggest sorafenib exposure and sorafenib-induced hyperbilirubinemia may be related to a (TA)5/6/7 repeat polymorphism in UGT1A1*28 (UGT, uridine glucuronosyl transferase). We hypothesized that sorafenib inhibits UGT1A1 and individuals carrying UGT1A1*28 and/or UGT1A9 variants experience greater sorafenib exposure and greater increase in sorafenib-induced plasma bilirubin concentration. Experimental Design: Inhibition of UGT1A1-mediated bilirubin glucuronidation by sorafenib was assessed in vitro. UGT1A1*28 and UGT1A9*3 genotypes were ascertained with fragment analysis or direct sequencing in 120 cancer patients receiving sorafenib on five different clinical trials. Total bilirubin measurements were collected in prostate cancer patients before receiving sorafenib (n = 41) and 19 to 30 days following treatment and were compared with UGT1A1*28 genotype. Results: Sorafenib exhibited mixed-mode inhibition of UGT1A1-mediated bilirubin glucuronidation (IC50 = 18 μmol/L; Ki = 11.7 μmol/L) in vitro. Five patients carrying UGT1A1*28/*28 (n = 4) or UGT1A9*3/*3 (n = 1) genotypes had first dose, dose-normalized areas under the sorafenib plasma concentration versus time curve (AUC) that were in the 93rd percentile, whereas three patients carrying UGT1A1*28/*28 had AUCs in the bottom quartile of all genotyped patients. The Drug Metabolizing Enzymes and Transporters genotyping platform was applied to DNA obtained from six patients, which revealed the ABCC2-24C>T genotype cosegregated with sorafenib AUC phenotype. Sorafenib exposure was related to plasma bilirubin increases in patients carrying 1 or 2 copies of UGT1A1*28 alleles (n = 12 and n = 5; R2 = 0.38 and R2 = 0.77; P = 0.032 and P = 0.051, respectively). UGT1A1*28 carriers showed two distinct phenotypes that could be explained by ABCC2-24C>T genotype and are more likely to experience plasma bilirubin increases following sorafenib if they had high sorafenib exposure. Conclusions: This pilot study indicates that genotype status of UGT1A1, UGT1A9, and ABCC2 and serum bilirubin concentration increases reflect abnormally high AUC in patients treated with sorafenib. Clin Cancer Res; 18(7); 2099–107. ©2012 AACR.

Clinical pharmacology and pharmacogenetics in a genomics era: the DMET platform

While no genome-wide pharmacogenetics study has yet been published, the field of pharmacogenetics is moving towards exploratory, large-scale analyses of the interaction between genetic variation and drug treatment. The Drug Metabolizing Enzymes and Transporters (DMET) platform offers a standardized set of 1936 variants in 225 genes related to drug absorption, distribution, metabolism and elimination that is useful to scan the genome for previously unknown associations between variation in absorption, distribution, metabolism and elimination genes and pharmacokinetic and pharmacodynamic outcomes of drug treatment. The purpose of this review is to put the DMET platform into context within the current study designs that have been used in pharmacogenetics, and to explore the role that DMET has played - and will play - in future pharmacogenetics studies.

Androgen Receptor CAG Repeat Length and Association With Prostate Cancer Risk: Results From the Prostate Cancer Prevention Trial

PURPOSE We investigated the association between the length of the polymorphic trinucleotide CAG microsatellite repeats in exon 1 of the AR gene and the risk of prostate cancer. MATERIALS AND METHODS This is a nested case-control study of 1,159 cases and 1,353 controls from the Prostate Cancer Prevention Trial, a randomized, placebo controlled trial testing whether the 5α-reductase inhibitor finasteride could decrease the 7-year prevalence of prostate cancer. During the course of the trial men underwent annual digital rectal examination and prostate specific antigen measurement. Prostate biopsy was recommended in all men with abnormal digital rectal examination or finasteride adjusted prostate specific antigen greater than 4.0 ng/ml. Cases were drawn from men with biopsy determined prostate cancer identified by for cause or end of study biopsy. Controls were selected from men who completed the end of study biopsy. RESULTS Mean CAG repeat length did not differ between cases and controls. The frequency distribution of cases and controls for the AR CAG repeat length was similar. There were no significant associations of CAG repeat length with prostate cancer risk when stratified by treatment arm (finasteride or placebo), or when combined. There was also no significant association between CAG repeat length and the risk of low or high grade prostate cancer. CONCLUSIONS There is no association of AR CAG repeat length with prostate cancer risk. Knowledge of AR CAG repeat length provides no clinically useful information to predict prostate cancer risk.

Disclosing a Diagnosis of Cancer: Where and How Does It Occur?

PURPOSE While disclosing a cancer diagnosis to a patient is common practice, how it is disclosed and the impact it has on the patient are poorly understood. We examined how cancer diagnoses were first given to patients and the impact of different aspects of disclosure on patient satisfaction. PATIENTS AND METHODS We provided a self-administered questionnaire to a total of 460 oncology patients of the National Cancer Institute (NCI) being treated at the National Institutes of Health (NIH) Clinical Center in Bethesda, MD. RESULTS Of the 437 patients who completed the survey, 54% were told their diagnosis in-person in the physicians office, 18% by phone, and 28% in the hospital. Forty-four percent of patients reported discussions of 10 minutes or fewer, 53% reported discussions lasting longer than 10 minutes, and 5% could not remember. Treatment options were not discussed for 31% of those who could clearly remember. Higher mean satisfaction scores were associated with diagnoses revealed in person rather than over the phone (68.2 +/- 1.6 v 47.2 +/- 3.7), diagnoses revealed in a personal setting rather than an impersonal setting (68.9 +/- 1.6 v 55.7 +/- 2.8), discussions lasting longer than 10 minutes rather than fewer than 10 minutes (73.5 +/- 1.9 v 54.1 +/- 2.4), and inclusion of treatment options rather than exclusion (72.0 +/- 1.9 v 50.7 +/- 3.2; P < .001 for each aspect). CONCLUSION Physicians should disclose a cancer diagnosis in a personal setting, discussing the diagnosis and treatment options for a substantial period of time whenever possible.

A SNP in CYP2C8 is not associated with the development of bisphosphonate-related osteonecrosis of the jaw in men with castrate-resistant prostate cancer.

A single nucleotide polymorphism (SNP) in CYP2C8 (rs1934951), was previously identified in a genome-wide association study as a risk factor for the development of osteonecrosis of the jaw (ONJ) in patients receiving bisphosphonates (BPs) for multiple myeloma. To determine if the same SNP is also associated with the development of ONJ in men receiving BPs for bone metastases from prostate cancer, we genotyped 100 men with castrate-resistant prostate cancer treated with bisphosphonates for bone metastases, 17 of whom developed ONJ. Important clinical characteristics, including type and duration of bisphosphonate therapy, were consistent among those who developed ONJ and those who did not. We found no significant correlation between the variant allele and the development of ONJ (OR = 0.63, 95% CI: 0.165–2.42, P > 0.47). This intronic SNP in CYP2C8 (rs1934951) does not seem to be a risk factor for the development of bisphosphonate-related ONJ in men with prostate cancer. It is important to note that this is only the second study to investigate the genetics associated with BP-related ONJ and the first to do so in men with prostate cancer. More studies are needed to identify genetic risk factors that may predict the development of this important clinical condition.

VEGF inhibition and metastasis: Possible implications for antiangiogenic therapy

Since the 2004 approval of bevacizumab, a humanized monoclonal antibody that binds vascular endothelial growth factor (VEGF), antiangiogenic therapy has been used to treat selected cancers, including colon, non-small cell lung, and breast cancers. In addition to bevacizumab, the FDA has approved two other antiangiogenic therapies; sorafenib and sunitinib, both of which are tyrosine kinase inhibitors that target VEGF receptors, particularly VEGFR2. However, even with the approval of these three drugs, antiangiogenic therapy has not yet had the impact some have hoped for. Many clinical benefits are short-lived; while numerous trials have shown an increase in survival in patients treated with antiangiogenic therapy, the increase for many was a matter of months.1 While any improvement in overall survival should be regarded as an accomplishment, it is important to understand why such clinical improvements are sometimes fleeting so that newer therapies can result in more enduring benefits.

Androgen receptor sequence and variations in several common prostate cancer cell lines

The androgen receptor gene (AR) plays an important role in molecular signaling and regulation and the subsequent cellular growth of prostate cancer. In addition, it is a highly variable region of the genome. We used direct nucleotide sequencing to genotype the entire exogenous coding region of the androgen receptor in ten commonly used prostate cancer cell lines. Our analysis confirmed the presence or absence of several known SNPs in the cell lines studied. We also assayed the number of CAG-repeat and GGC-repeat sequences for each for the ten cell lines. Our analysis identified three new mutations, one each in the DU145, LnCAP, and RWPE-2 cell lines. In DU145, the DNA isolated in our lab was heterozygous at G527G (T>C transition), a polymorphism not previously reported. The LnCAP cells cultured in our lab were found to have a T>C transition (heterozygous), resulting in a S641P change that was not present in the ATCC cell line DNA. Lastly, a homozygous G>T transversion was found in RWPE-2 cells, resulting in the S187I change. This is potentially significant for use in cell culture and future cell model development.

High-Throughput Platforms in Drug Metabolism and Transport Pharmacogenetics

Although there are now several thousand published studies that have examined the genetic contribution to interindividual variation in drug treatment (i.e., pharmacogenetics), very few have examined the large portions of the genome; rather these have focused on candidate gene and pathway-based study designs. However, multiple large-scale genotyping technologies have recently emerged that allow the researcher to examine pharmacogenetic endpoints ~100–500,000 SNPs at a time. Each genotyping platform is slightly different and applicable to either the clinical setting, wherein the genetic information informs treatment in patients with certain variants, or the research setting, where patients that are treated with certain drugs are either prospectively or retrospectively evaluated for genetic variants that may influence treatment outcomes. The purpose of this chapter is to describe the current study designs in pharmacogenetics, the major findings of these studies that are applied clinically, to provide an overview of commercially available large-scale genotyping technologies, and to discuss how these technologies can be applied in both clinical and research settings. While oncology agents will be the primary focus of this chapter, given that individuals undergoing therapy for cancer are often treated with multiple drugs, it is important to also consider other agents.