Citations

Abstract Purpose: To determine the maximum tolerated dose (MTD), characterize the principal toxicities, and assess the pharmacokinetics of EKB-569, an oral selective irreversible inhibitor of the epidermal growth factor receptor tyrosine kinase, in combination with capecitabine in patients with advanced colorectal cancer. Experimental Design: Patients were treated with EKB-569 daily for 21 days and capecitabine twice daily for 14 days of a 21-day cycle. The dose levels of EKB-569 (mg/day) and capecitabine (mg/m2 twice daily) assessed were 25/750, 50/750, 50/1,000 and 75/1,000. An expanded cohort was enrolled at the MTD to better study toxicity and efficacy. Samples of plasma were collected to characterize the pharmacokinetics of the agents. Treatment efficacy was assessed every other cycle. Results: A total of 37 patients, the majority of whom had prior chemotherapy, received a total of 163 cycles of treatment. Twenty patients were treated at the MTD, 50 mg EKB-569, daily and 1,000 mg/m2 capecitabine twice daily. Dose-limiting toxicities were diarrhea and rash. No patients had complete or partial responses but 48% had stable disease. The conversion of capecitabine to 5-fluorouracil was higher for the combination of EKB-569 and capecitabine (321 ± 151 ng*h/mL) than for capecitabine alone (176 ± 62 ng*hours/mL; P = 0.0037). Conclusion: In advanced colorectal cancer, 50 mg EKB-569 daily can be safely combined with 1,000 mg/m2 capecitabine twice a day. A statistically significant increase in plasma levels of 5-fluorouracil for the combination of EKB-569 and capecitabine may be due to the single-dose versus multiple-dose exposure difference, variability in exposure or a potential drug interaction.

Abstract Two cytidine analogues, gemcitabine (dFdC) and 1-β-d-arabinofuranosylcytosine (AraC), show significant therapeutic effect in a variety of cancers. However, response to these drugs varies widely. Evidence from tumor biopsy samples shows that expression levels for genes involved in the cytidine transport, metabolism, and bioactivation pathway contribute to this variation in response. In the present study, we set out to test the hypothesis that variation in gene expression both within and outside of this “pathway” might influence sensitivity to gemcitabine and AraC. Specifically, Affymetrix U133 Plus 2.0 GeneChip and cytotoxicity assays were performed to obtain basal mRNA expression and IC50 values for both drugs in 197 ethnically defined Human Variation Panel lymphoblastoid cell lines. Genes with a high degree of association with IC50 values were involved mainly in cell death, cancer, cell cycle, and nucleic acid metabolism pathways. We validated selected significant genes by performing real-time quantitative reverse transcription-PCR and selected two representative candidates, NT5C3 (within the pathway) and FKBP5 (outside of the pathway), for functional validation. Those studies showed that down-regulation of NT5C3 and FKBP5 altered tumor cell sensitivity to both drugs. Our results suggest that cell-based model system studies, when combined with complementary functional characterization, may help to identify biomarkers for response to chemotherapy with these cytidine analogues. [Cancer Res 2008;68(17):7050–8]

Abstract A recent genome-wide association study found that genetic variants on chromosomes 3, 6, 7, 10, 11, 19 and X were associated with prostate cancer risk. We evaluated the most significant single-nucleotide polymorphisms (SNP) in these loci using a worldwide consortium of 13 groups (PRACTICAL). Blood DNA from 7,370 prostate cancer cases and 5,742 male controls was analyzed by genotyping assays. Odds ratios (OR) associated with each genotype were estimated using unconditional logistic regression. Six of the seven SNPs showed clear evidence of association with prostate cancer (P = 0.0007-P = 10−17). For each of these six SNPs, the estimated per-allele OR was similar to those previously reported and ranged from 1.12 to 1.29. One SNP on 3p12 (rs2660753) showed a weaker association than previously reported [per-allele OR, 1.08 (95% confidence interval, 1.00-1.16; P = 0.06) versus 1.18 (95% confidence interval, 1.06-1.31)]. The combined risks associated with each pair of SNPs were consistent with a multiplicative risk model. Under this model, and in combination with previously reported SNPs on 8q and 17q, these loci explain 16% of the familial risk of the disease, and men in the top 10% of the risk distribution have a 2.1-fold increased risk relative to general population rates. This study provides strong confirmation of these susceptibility loci in multiple populations and shows that they make an important contribution to prostate cancer risk prediction. (Cancer Epidemiol Biomarkers Prev 2008;17(8):2052–61)

Abstract Catechol O-methyltransferase (COMT)-catalyzed methylation of catecholestrogens has been proposed to play a protective role in estrogen-induced genotoxic carcinogenesis. We have taken a comprehensive approach to test the hypothesis that genetic variation in COMT might influence breast cancer risk. Fifteen COMT single nucleotide polymorphisms (SNPs) selected on the basis of in-depth resequencing of the COMT gene were genotyped in 1,482 DNA samples from a Mayo Clinic breast cancer case control study. Two common SNPs in the distal promoter for membrane-bound (MB) COMT, rs2020917 and rs737865, were associated with breast cancer risk reduction in premenopausal women in the Mayo Clinic study, with allele-specific odds ratios (OR) of 0.70 [95% confidence interval (CI), 0.52–0.95] and 0.68 (95% CI, 0.51–0.92), respectively. These two SNPs were then subjected to functional genomic analysis and were genotyped in an additional 3,683 DNA samples from two independent case control studies (GENICA and GESBC). Functional genomic experiments showed that these SNPs could up-regulate transcription and that they altered DNA-protein binding patterns. Furthermore, substrate kinetic and exon array analyses suggested a role for MB-COMT in catecholestrogen inactivation. The GENICA results were similar to the Mayo case control observations, with ORs of 0.85 (95% CI, 0.72–1.00) and 0.85 (95% CI, 0.72–1.01) for the two SNPs. No significant effect was observed in the GESBC study. These studies showed that two SNPs in the COMT distal promoter were associated with breast cancer risk reduction in two of three case control studies, compatible with the results of functional genomic experiments, suggesting a role for MB-COMT in breast cancer risk. [Cancer Res 2008;68(14):5997–6005]

Object The cervical foraminotomy was pioneered in the 1940s to address radicular symptoms via a posterior approach, but the long-term outcome has not been adequately studied. Methods The authors retrospectively analyzed data obtained from 303 patients (188 male and 115 female, mean age 49.2 years) who had consecutively undergone a single-level posterior foraminotomy for cervical radiculopathy between 1972 and 1992. The median follow-up duration was 7.1 years. The major end point studied was the development of symptomatic adjacent- or same-segment disease. Incidence rates per 1000 person-years were calculated, and the natural history of the disease was predicted using Kaplan–Meier survivorship analysis. In 15 (4.9%) of 303 patients, symptomatic adjacent-segment disease developed, yielding a rate of 6.4/1000 person-years at risk. This included nine (2.9%) of 303 patients requiring reoperation, yielding a rate of 3.8/1000 person-years. Kaplan–Meier survivorship analysis suggested a relatively stable annual 0.7% rate for developing adjacent-segment disease, with a 10-year rate of 6.7%. Ten patients developed same-segment disease, yielding a risk rate of 3.9/1000 person-years. Kaplan–Meier survivorship analysis demonstrated a 5- and 10-year risk rate of developing same-segment disease of 3.2 and 5.0%, respectively. Conclusions Although additional study is needed, analysis of the present data suggests that posterior foraminotomy is associated with a low rate of same- and adjacent-segment disease.

Object Thyroid-stimulating hormone (TSH)–secreting pituitary adenomas are rare, representing < 2% of all pituitary adenomas. Methods The authors conducted a retrospective analysis of patients with TSH-secreting or clinically silent TSH-immunostaining pituitary tumors among all pituitary adenomas followed at their institution between 1987 and 2003. Patient records, including clinical, imaging, and pathological and surgical characteristics were reviewed. Twenty-one patients (6 women and 15 men; mean age 46 years, range 26–73 years) were identified. Of these, 10 patients had a history of clinical hyperthyroidism, of whom 7 had undergone ablative thyroid procedures (thyroid surgery/131I ablation) prior to the diagnosis of pituitary adenoma. Ten patients had elevated TSH preoperatively. Seven patients presented with headache, and 8 presented with visual field defects. All patients underwent imaging, of which 19 were available for imaging review. Sixteen patients had macroadenomas. Results Of the 21 patients, 18 underwent transsphenoidal surgery at the authors' institution, 2 patients underwent transsphenoidal surgery at another facility, and 1 was treated medically. Patients with TSH-secreting tumors were defined as in remission after surgery if they had no residual adenoma on imaging and had biochemical evidence of hypo-or euthyroidism. Patients with TSH-immunostaining tumors were considered in remission if they had no residual tumor. Of these 18 patients, 9 (50%) were in remission following surgery. Seven patients had residual tumor; 2 of these patients underwent further transsphenoidal resection, 1 underwent a craniotomy, and 4 underwent postoperative radiation therapy (2 conventional radiation therapy, 1 Gamma Knife surgery, and 1 had both types of radiation treatment). Two patients had persistently elevated TSH levels despite the lack of evidence of residual tumor. On pathological analysis and immunostaining of the surgical specimen, 17 patients had samples that stained positively for TSH, 8 for α-subunit, 10 for growth hormone, 7 for prolactin, 2 for adrenocorticotrophic hormone, and 1 for follicle-stimulating hormone/luteinizing hormone. Eleven patients (61%) ultimately required thyroid hormone replacement therapy, and 5 (24%) required additional pituitary hormone replacement. Of these, 2 patients required treatment for new anterior pituitary dysfunction as a complication of surgery, and 2 patients with preoperative partial anterior pituitary dysfunction developed complete panhypopituitarism. One patient had transient diabetes insipidus. The remainder had no change in pituitary function from their preoperative state. Conclusions Thyroid-stimulating hormone–secreting pituitary lesions are often delayed in diagnosis, are frequently macroadenomas and plurihormonal in terms of their pathological characteristics, have a heterogeneous clinical picture, and are difficult to treat. An experienced team approach will optimize results in the management of these uncommon lesions.

Abstract Purpose: Hyperactivation of the phosphatidylinositol 3-kinase/Akt signaling through disruption of PTEN function is common in glioblastoma multiforme, and these genetic changes are predicted to enhance sensitivity to mammalian target of rapamycin (mTOR) inhibitors such as RAD001 (everolimus). Experimental Design: To test whether PTEN loss could be used as a predictive marker for mTOR inhibitor sensitivity, the response of 17 serially transplantable glioblastoma multiforme xenografts was evaluated in an orthotopic therapy evaluation model. Of these 17 xenograft lines, 7 have either genomic deletion or mutation of PTEN. Results: Consistent with activation of Akt signaling, there was a good correlation between loss of PTEN function and elevated levels of Akt phosphorylation. However, of the 7 lines with disrupted PTEN function, only 1 tumor line (GBM10) was significantly sensitive to RAD001 therapy (25% prolongation in median survival), whereas 1 of 10 xenograft lines with wild-type PTEN was significantly sensitive to RAD001 (GS22; 34% prolongation in survival). Relative to placebo, 5 days of RAD001 treatment was associated with a marked 66% reduction in the MIB1 proliferation index in the sensitive GBM10 line (deleted PTEN) compared with a 25% and 7% reduction in MIB1 labeling index in the insensitive GBM14 (mutant PTEN) and GBM15 (wild-type PTEN) lines, respectively. Consistent with a cytostatic antitumor effect, bioluminescent imaging of luciferase-transduced intracranial GBM10 xenografts showed slowed tumor growth without significant tumor regression during RAD001 therapy. Conclusion: These data suggest that loss of PTEN function is insufficient to adequately predict responsiveness to mTOR inhibitors in glioblastoma multiforme.

Abstract Glutathione S-transferase P1 (GSTP1) is of importance for cancer research because of its role in detoxifying carcinogens, activating antineoplastic prodrugs, metabolizing chemotherapeutic agents, and its involvement in cell cycle and apoptosis regulation. Two common GSTP1 genetic polymorphisms have been studied extensively. However, the full range of GSTP1 genetic variation has not been systematically characterized in the absence of disease pathology. We set out to identify common GSTP1 polymorphisms in four ethnic groups, followed by functional genomic studies. All exons, splice junctions, and the 5′-flanking region of GSTP1 were resequenced using 60 DNA samples each from four ethnic groups. The 35 single-nucleotide polymorphisms (SNP) identified included six nonsynonymous SNPs and 17 previously unreported polymorphisms. GSTP1 variant allozymes were then expressed in COS-1 cells, and five displayed significantly altered levels of enzyme activity. One decreased to 22% of the wild-type (WT) activity. Four variant allozymes had Km values that differed significantly from that of the WT, and five showed altered levels of immunoreactive protein compared with WT, with a significant correlation (r = 0.79, P &lt; 0.007) between levels of immunoreactive protein and enzyme activity in these samples. In the Mexican American population, five linked SNPs were significantly associated with GSTP1 mRNA expression, one of which was found by electrophoretic mobility shift assay to alter protein binding. These studies have identified functionally significant genetic variation, in addition to the two frequently studied GSTP1 nonsynonymous SNPs, that may influence GSTP1's contribution to carcinogen and drug metabolism, and possibly disease pathogenesis and/or drug response. [Cancer Res 2008;68(12):4791–801]

Abstract Purpose: The proteasome is a multisubunit cellular organelle that functions as a nonlysosomal threonine protease. Proteasomes play a critical role in the degradation of proteins, regulating a variety of cellular processes, and they are also the target for antineoplastic proteasome inhibitors. Genetic variation in proteasome subunits could influence both proteasome function and response to drug therapy. Experimental Design: We resequenced genes encoding the three active proteasome β subunits using 240 DNA samples from four ethnic groups and the β5 subunit gene in 79 DNA samples from multiple myeloma patients who had been treated with the proteasome inhibitor bortezomib. Resequencing was followed by functional studies of polymorphisms identified in the coding region and 3′-flanking region (3′-FR) of PSMB5, the gene encoding the target for clinically useful proteasome inhibitors. Results: Resequencing of 240 DNA samples identified a series of novel ethnic-specific polymorphisms that are not represented in public databases. The PSMB5 3′-FR 1042 G allele significantly increased transcription during reporter gene studies, observations confirmed by genotype-phenotype correlations between single nucleotide polymorphisms (SNP) in PSMB5 and mRNA expression in the 240 lymphoblastoid cell lines from which the resequenced DNA was obtained. Studies with patient DNA samples identified additional novel PSMB5 polymorphisms, including a SNP and an insertion in the 3′-FR. Reporter-gene studies indicated that these two novel polymorphisms might decrease transcription. Conclusions: These results show that nonsynonymous coding SNPs in the PSMB5 gene did not show significant effects on proteasome activity, but SNPs did influence transcription. Future studies might focus on regulatory region polymorphisms.