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Utility of PTEN protein dosage in predicting for underlying germline PTEN mutations among patients presenting with thyroid cancer and Cowden-like phenotypes.

ABSTRACT: Thyroid cancer is a major component of Cowden syndrome (CS). CS patients with an underlying PTEN mutation (PTEN(mut+)) have a 70-fold increased risk of developing epithelial thyroid cancer. In contrast, less than 1% of sporadic epithelial thyroid cancer patients carry a germline PTEN mutation. Cost-efficient markers capable of shortlisting thyroid cancers for CS genetic testing would be clinically useful.Our objective was to analyze the utility of patient blood phosphate and tensin homolog deleted on chromosome 10 (PTEN) protein levels in predicting germline PTEN mutations.We conducted a 5-yr, multicenter prospective study of 2792 CS and CS-like patients, all of whom had comprehensive PTEN analysis. Analysis of PTEN and downstream proteins by immunoblotting was performed on total protein lysates from patient-derived lymphoblast lines. We compared blood PTEN protein levels between PTEN(mut+) patients and those with variants of unknown significance or wild-type PTEN (PTEN(wt/vus)).We assessed the utility of PTEN protein levels in predicting germline PTEN mutations.Of 2792 CS/CS-like patients, 721 patients had thyroid cancer; 582 of them (81%) had blood PTEN protein analyzed. PTEN germline pathogenic mutations were present in 27 of 582 patients (4.6%). Ninety-six percent (26 of 27) of PTEN(mut+) patients had blood PTEN protein levels in the lowest quartile as compared with 25% (139 of 555) of PTEN(wt/vus) patients (P < 0.001). Low blood PTEN levels predicted for PTEN(mut+) cases with a 99.76% negative predictive value (95% confidence interval = 98.67-99.96) and a positive test likelihood ratio of 3.84 (95% confidence interval = 3.27-4.52).Our study shows that low blood PTEN protein expression could serve as a screening molecular correlate to predict for germline PTEN mutation in CS and CS-like presentations of thyroid cancer.

SUBMITTER: Ngeow J

PROVIDER: S-EPMC3513537 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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Utility of PTEN protein dosage in predicting for underlying germline PTEN mutations among patients presenting with thyroid cancer and Cowden-like phenotypes.

Ngeow Joanne J He Xin X Mester Jessica L JL Lei Junying J Romigh Todd T Orloff Mohammed S MS Milas Mira M Eng Charis C

The Journal of clinical endocrinology and metabolism 20121012 12

<h4>Context</h4>Thyroid cancer is a major component of Cowden syndrome (CS). CS patients with an underlying PTEN mutation (PTEN(mut+)) have a 70-fold increased risk of developing epithelial thyroid cancer. In contrast, less than 1% of sporadic epithelial thyroid cancer patients carry a germline PTEN mutation. Cost-efficient markers capable of shortlisting thyroid cancers for CS genetic testing would be clinically useful.<h4>Objective</h4>Our objective was to analyze the utility of patient blood ...[more]

PMID: 23066114

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Project description:Patients with heritable cancer syndromes characterized by germline PTEN mutations (termed PTEN hamartoma tumor syndrome, PHTS) benefit from PTEN-enabled cancer risk assessment and clinical management. PTEN-wildtype patients (~50%) remain at increased risk of developing certain cancers. Existence of germline mutations in other known cancer susceptibility genes has not been explored in these patients, with implications for different medical management. We conducted a 4-year multicenter prospective study of incident patients with features of Cowden/Cowden-like (CS/CS-like) and Bannayan-Riley-Ruvalcaba syndromes (BRRS) without PTEN mutations. Exome sequencing and targeted analysis were performed including 59 clinically actionable genes from the American College of Medical Genetics and Genomics (ACMG) and 24 additional genes associated with inherited cancer syndromes. Pathogenic or likely pathogenic cancer susceptibility gene alterations were found in 7 of the 87 (8%) CS/CS-like and BRRS patients and included MUTYH, RET, TSC2, BRCA1, BRCA2, ERCC2 and HRAS. We found classic phenotypes associated with the identified genes in 5 of the 7 (71.4%) patients. Variant positive patients were enriched for the presence of second malignant neoplasms compared to patients without identified variants (OR = 6.101, 95% CI 1.143-35.98, p = 0.035). Germline variant spectrum and frequencies were compared to The Cancer Genome Atlas (TCGA), including 6 apparently sporadic cancers associated with PHTS. With comparable overall prevalence of germline variants, the spectrum of mutated genes was different in our patients compared to TCGA. Intriguingly, we also found notable enrichment of variants of uncertain significance (VUS) in our patients (OR = 2.3, 95% CI 1.5-3.5, p = 0.0002). Our data suggest that only a small subset of PTEN-wildtype CS/CS-like and BRRS patients could be accounted for by germline variants in some of the known cancer-related genes. Thus, the existence of alterations in other and more likely non-classic cancer-associated genes is plausible, reflecting the complexity of these heterogeneous hereditary cancer syndromes.

Project description:Cowden syndrome (CS), a Mendelian autosomal-dominant disorder, predisposes to breast, thyroid and other cancers. Germline mutations in phosphatase and tensin homolog (PTEN) have been recently reported in 23% of a large series of classic CS. Here, we validated our small (n = 10) pilot study in a large patient series that germline variations in succinate dehydrogenase genes (SDHx) occur in 8% (49/608) of PTEN mutation-negative CS and CS-like (CSL) individuals (SDH(var+)). None of these SDHx variants was found in 700 population controls (P < 0.0001). We then found that SDHx variants also occur in 6% (26/444) of PTEN mutation-positive (PTEN(mut+)) CS/CSL individuals (PTEN(mut+)/SDH(var+)). Of 22 PTEN(mut+)/SDH(var+) females, 17 had breast cancers compared with 34/105 PTEN(mut+) (P < 0.001) or 27/47 SDH(var+) patients (P = 0.06). Notably, individuals with SDH(var+) alone had the highest thyroid cancer prevalence (24/47) compared with PTEN(mut+) patients (27/105, P = 0.002) or PTEN(mut+)/SDH(var+) carriers (6/22, P = 0.038). Patient-derived SDH(var+) lymphoblastoid cells had elevated cellular reactive oxygen species, highest in PTEN(mut+)/SDH(var+) cells, correlating with apoptosis resistance. SDH(var+) cells showed stabilized and hyperactivated hypoxia inducible factor (HIF)1? signaling. Most interestingly, we also observed the loss of steady-state p53 in the majority of SDH(var+) cells. This loss of p53 was regulated by MDM2-independent NADH quinone oxidoreductase 1-mediated protein degradation, likely due to the imbalance of flavin adenine dinucleotide/nicotinamide adenine dinucleotide in SDH(var+) cells. Our data suggest the potential regulation of HIF1?, p53 and PTEN signaling by mitochondrial metabolism in CS/CSL tumorigenesis. Together, our findings suggest the importance of considering SDHx as candidate predisposing and modifier genes for CS/CSL-related malignancy risks, and a mechanism which suggests ways of therapeutic reversal or prevention.

Dataset Information

Utility of PTEN protein dosage in predicting for underlying germline PTEN mutations among patients presenting with thyroid cancer and Cowden-like phenotypes.

Publications

Utility of PTEN protein dosage in predicting for underlying germline PTEN mutations among patients presenting with thyroid cancer and Cowden-like phenotypes.

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