A retrospective analysis of RET translocation, gene copy number gain and expression in NSCLC patients treated with vandetanib in four randomized Phase III studies.

BACKGROUND: To determine the prevalence of RET rearrangement genes, RET copy number gains and expression in tumor samples from four Phase III non-small-cell lung cancer (NSCLC) trials of vandetanib, a selective inhibitor of VEGFR, RET and EGFR signaling, and to determine any association with outcome to vandetanib treatment. METHODS: Archival tumor samples from the ZODIAC ( NCT00312377 , vandetanib ± docetaxel), ZEAL ( NCT00418886 , vandetanib ± pemetrexed), ZEPHYR ( NCT00404924 , vandetanib vs placebo) and ZEST ( NCT00364351 , vandetanib vs erlotinib) studies were evaluated by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) in 944 and 1102 patients. RESULTS: The prevalence of RET rearrangements by FISH was 0.7% (95% CI 0.3-1.5%) among patients with a known result. Seven tumor samples were positive for RET rearrangements (vandetanib, n = 3; comparator, n = 4). 2.8% (n = 26) of samples had RET amplification (innumerable RET clusters, or ≥7 copies in > 10% of tumor cells), 8.1% (n = 76) had low RET gene copy number gain (4-6 copies in ≥40% of tumor cells) and 8.3% (n = 92) were RET expression positive (signal intensity ++ or +++ in >10% of tumor cells). Of RET-rearrangement-positive patients, none had an objective response in the vandetanib arm and one patient responded in the comparator arm. Radiologic evidence of tumor shrinkage was observed in two patients treated with vandetanib and one treated with comparator drug. The objective response rate was similar in the vandetanib and comparator arms for patients positive for RET copy number gains or RET protein expression. CONCLUSIONS: We have identified prevalence for three RET biomarkers in a population predominated by non-Asians and smokers. RET rearrangement prevalence was lower than previously reported. We found no evidence of a differential benefit for efficacy by IHC and RET gene copy number gains. The low prevalence of RET rearrangements (0.7%) prevents firm conclusions regarding association of vandetanib treatment with efficacy in the RET rearrangement NSCLC subpopulation. TRIAL REGISTRATION: Randomized Phase III clinical trials ( NCT00312377 , ZODIAC; NCT00418886 , ZEAL; NCT00364351 , ZEST; NCT00404924 , ZEPHYR).

Characterization of a naturally-occurring polymorphism in the UHR-1 gene encoding the putative rat prolactin-releasing peptide receptor.

The rat orphan receptor UHR-1 and its human orthologue, GPR10, were first isolated in 1995. The ligand for this receptor, prolactin-releasing peptide (PrRP), was identified in 1998 by reverse pharmacology and has subsequently been implicated in a number of physiological processes. As supported by its localization and regulation in the hypothalamus and brainstem, we have shown previously that PrRP is involved in energy homeostasis. Here we describe a naturally occurring polymorphism in the UHR-1 gene that results in an ATG to ATA change at the putative translational initiation site. The presence of the polymorphism abolished the binding of 125I PrRP in rat brain slices but did not affect the ability of PrRP to reduce fast-induced food intake. Together this data suggest that PrRP may be exerting its feeding effects through a receptor other than UHR-1.

Occurrence and pharmacological characterization of four human tachykinin NK2 receptor variants.

Tachykinin NK(2) receptor antagonists are potentially beneficial in treating various disorders including irritable bowel syndrome, urinary incontinence, depression and anxiety. The current study evaluates the frequency of single nucleotide polymorphisms (SNPs) in the human NK(2) receptor gene (TACR2). In addition, the potency of the endogenous peptide agonist neurokinin A (NKA), and the small molecule antagonists saredutant (NK(2)-selective) and ZD6021 (pan-NK antagonist) at the various NK(2) receptor protein variants were determined. The TACR2 gene was sequenced from 37 individuals. Two amino acid changing SNPs encoding the NK(2) receptor variants Ile23Thr and Arg375His were found. The frequency of the four possible protein variants differed between populations. Site-directed mutagenesis was performed introducing either SNP or both SNPs into the TACR2 gene and the constructs were transfected into CHO cells. NKA-evoked increases in intracellular Ca(2+) were monitored by FLIPR. The potency of saredutant and ZD6021 was evaluated by their ability to inhibit NKA-induced increases in intracellular Ca(2+). NKA evoked increases in intracellular Ca(2+) with a potency ranging between 1 and 5nM in CHO cells expressing the different constructs. Saredutant and ZD6021 blocked NKA-evoked increases in intracellular Ca(2+) with pK(b) values ranging between 8.8-9.3 and 7.9-8.7, respectively. The current study demonstrates that polymorphisms leading to the Ile23Thr and Arg375His amino acid exchanges are highly prevalent in the human TACR2 gene. These polymorphisms however do not appear to affect the potency of the endogenous agonist NKA or the small molecule antagonists saredutant and ZD6021 with respect to intracellular Ca(2+) signalling.

A stop codon mutation in SCN9A causes lack of pain sensation.

The general lack of pain experience is a rare occurrence in humans, and the molecular causes for this phenotype are not well understood. Here we have studied a Canadian family from Newfoundland with members who exhibit a congenital inability to experience pain. We have mapped the locus to a 13.7 Mb region on chromosome 2q (2q24.3-2q31.1). Screening of candidate genes in this region identified a protein-truncating mutation in SCN9A, which encodes for the voltage-gated sodium channel Na(v)1.7. The mutation is a C-A transversion at nucleotide 984 transforming the codon for tyrosine 328 to a stop codon. The predicted product lacks all pore-forming regions of Na(v)1.7. Indeed, expression of this altered gene in a cell line did not produce functional responses, nor did it cause compensatory effects on endogenous voltage-gated sodium currents when expressed in ND7/23 cells. Because a homozygous knockout of Na(v)1.7 in mice has been shown to be lethal, we explored why a deficiency of Na(v)1.7 is non-lethal in humans. Expression studies in monkey, human, mouse and rat tissue indicated species-differences in the Na(v)1.7 expression profile. Whereas in rodents the channel was strongly expressed in hypothalamic nuclei, only weak mRNA levels were detected in this area in primates. Furthermore, primate pituitary and adrenal glands were devoid of signal, whereas these two glands were mRNA-positive in rodents. This species difference may explain the non-lethality of the observed mutation in humans. Our data further establish Na(v)1.7 as a critical element of peripheral nociception in humans.

Sequence variants in the melatonin-related receptor gene (GPR50) associate with circulating triglyceride and HDL levels.

The gene encoding the melatonin-related receptor (GPR50) is highly expressed within hypothalamic nuclei concerned with the control of body weight and metabolism. We screened GPR50 for mutations in an obese cohort and identified an insertion of four amino acid residues (TTGH) at position 501, two common coding polymorphisms (T528A and V602I), and one noncoding polymorphism (C-16X2GPR50T). Single-nucleotide polymorphisms were then typed in 500 English Caucasian subjects, and associations were sought to intermediate obesity phenotypes. Although no association was seen with body mass index, carriers of two copies of the mutant allele at C-16X2GPR50T, Ins501Del, and A1582G had significantly higher fasting circulating triglyceride levels (P < 0.05). In a separate set of 585 subjects, the associations were replicated, with statistically significant effects of similar magnitude and direction. The association of C-16X2GPR50T with fasting triglycerides was highly significant (P < 0.001). In addition, a significant association between C-16X2GPR50T and circulating HDL levels was observed in the combined population, with C-16X2GPR50T carriers having significantly lower circulating HDL-cholesterol levels (1.39 mM) than wild-type subjects (1.47 mM) (P < 0.01). These findings suggest a previously unexpected role for this orphan receptor in the regulation of lipid metabolism that warrants further investigation.

A major locus conferring susceptibility to infection by Streptococcus pneumoniae in mice.

We have studied the genetics of susceptibility to infection by Streptococcus pneumoniae in mice. Linkage analysis of the F(2) generation from a cross between resistant BALB/cO1aHsd and susceptible CBA/CaO1aHsd strains allowed us to map a major locus controlling the development of bacteremia and survival after intranasal infection.