Gene and protein expression markers of response to combined antiangiogenic and epidermal growth factor targeted therapy in renal cell carcinoma

BACKGROUND

Metastatic renal cell carcinoma (mRCC) patients treated with anti-vascular endothelial growth factor (VEGF) therapies demonstrate promising outcomes but not all patients benefit. Factors that predict response remain to be elucidated.

PATIENTS AND METHODS

Nephrectomy material from 37 patients with mRCC receiving bevacizumab +/- erlotinib was used for protein and gene expression assessment. Protein lysates were subjected to reverse-phase protein array profiling. RNA extracts were used to carry out gene expression microarray-based profiling. Normalized protein and gene expression data were correlated with overall survival (OS) and progression-free survival (PFS) using univariate Cox hazard model and linear regression. Immunoblotting was carried out to validate the results.

RESULTS

High protein levels of AMP-activated protein kinase and low levels of cyclin B1 (CCNB1) were associated with longer OS and PFS. Further validation revealed reduced expression and activation of phosphoinositide 3-kinase (PI3K) pathway components and cell cycle factors in patients with prolonged survival after therapy. Gene expression analysis revealed up-regulation of PI3K- and cell cycle-related pathways in patients with shorter PFS.

CONCLUSIONS

The OS and PFS of bevacizumab +/- erlotinib-treated patients with renal cell carcinoma were associated with changes in expression of protein and gene expression markers related to PI3K pathway and cell cycle signaling.

Genome-wide scan identifies novel modifier loci of acromegalic phenotypes for isolated familial somatotropinoma

Isolated familial somatotropinoma (IFS) accounts for 18% of familial isolated pituitary adenoma (FIPA) cases. Recently, germline mutations of the aryl hydrocarbon receptor-interacting protein gene (AIP) have been found in families with pituitary adenoma predisposition, FIPA, and IFS. In this study, we investigate the AIP mutation status and perform a genome-wide scan to search for the modifier regions of acromegalic phenotypes in an IFS family of 31 aborigines from Borneo. Complete endocrine diagnosis and data could not be collected due to logistical and cultural reasons. AIP mutation screening was carried out by direct sequencing and the genome-wide scan was performed using 400 microsatellites. Non-parametric linkage analysis was performed to obtain the logarithm of odds (LOD) scores. A novel AIP frameshift mutation in exon 4 (c.500delC) (p.P167HfsX3) was identified in all members with acromegalic features, as well as in 15 members without acromegalic features, revealing incomplete penetrance of AIP. The data showed that patients with the same mutation may express acromegalic features of differing severity, suggesting the existence of modifier genes. The highest LOD score of 2.2 was obtained near D19S571 (19q13.41). We also found weak linkages on chromosomes 3q28, 8q12.1, and 21q22.13, with LOD scores of 1.1, 1.8, and 1.4 respectively. Our results show the first genome-wide scan that identifies novel modifier loci for acromegalic phenotypes in an IFS family. Identification of modifier loci may provide further insight into the disease mechanism and explain the clinical variability observed in its patients.

HRPT2 mutations are associated with malignancy in sporadic parathyroid tumours

BACKGROUND

Hyperparathyroidism is a common endocrinopathy characterised by the formation of parathyroid tumours. In this study, we determine the role of the recently identified gene, HRPT2, in parathyroid tumorigenesis.

METHODS

Mutation analysis of HRPT2 was undertaken in 60 parathyroid tumours: five HPT-JT, three FIHP, three MEN 1, one MEN 2A, 25 sporadic adenomas, 17 hyperplastic glands, two lithium associated tumours, and four sporadic carcinomas. Loss of heterozygosity at 1q24-32 was performed on a subset of these tumours.

RESULTS

HRPT2 somatic mutations were detected in four of four sporadic parathyroid carcinoma samples, and germline mutations were found in five of five HPT-JT parathyroid tumours (two families) and two parathyroid tumours from one FIHP family. One HPT-JT tumour with germline mutation also harboured a somatic mutation. In total, seven novel and one previously reported mutation were identified. "Two-hits" (double mutations or one mutation and loss of heterozygosity at 1q24-32) affecting HRPT2 were found in two sporadic carcinomas, two HPT-JT-related and two FIHP related tumours.

CONCLUSIONS

The results in this study support the role of HRPT2 as a tumour suppressor gene in sporadic parathyroid carcinoma, and provide further evidence for HRPT2 as the causative gene in HPT-JT, and a subset of FIHP. In light of the strong association between mutations of HRPT2 and sporadic parathyroid carcinoma demonstrated in this study, it is hypothesised that HRPT2 mutation is an early event that may lead to parathyroid malignancy and suggest intragenic mutation of HRPT2 as a marker of malignant potential in both familial and sporadic parathyroid tumours.

HRPT2, encoding parafibromin, is mutated in hyperparathyroidism-jaw tumor syndrome

We report here the identification of a gene associated with the hyperparathyroidism-jaw tumor (HPT-JT) syndrome. A single locus associated with HPT-JT (HRPT2) was previously mapped to chromosomal region 1q25-q32. We refined this region to a critical interval of 12 cM by genotyping in 26 affected kindreds. Using a positional candidate approach, we identified thirteen different heterozygous, germline, inactivating mutations in a single gene in fourteen families with HPT-JT. The proposed role of HRPT2 as a tumor suppressor was supported by mutation screening in 48 parathyroid adenomas with cystic features, which identified three somatic inactivating mutations, all located in exon 1. None of these mutations were detected in normal controls, and all were predicted to cause deficient or impaired protein function. HRPT2 is a ubiquitously expressed, evolutionarily conserved gene encoding a predicted protein of 531 amino acids, for which we propose the name parafibromin. Our findings suggest that HRPT2 is a tumor-suppressor gene, the inactivation of which is directly involved in predisposition to HPT-JT and in development of some sporadic parathyroid tumors.