USP8 mutations in corticotroph adenomas determine a distinct gene expression profile irrespective of functional tumour status

OBJECTIVE

Pituitary corticotroph adenomas commonly cause Cushing's disease (CD) but part of these tumours are hormonally inactive (silent corticotroph adenomas, SCA). USP8 mutations are well-known driver mutations in corticotrophinomas. Differences in transcriptomic profiles between functioning and silent tumours or tumours with different USP8 status have not been investigated.

DESIGN AND METHODS

Forty-eight patients (28 CD, 20 SCA) were screened for USP8 mutations with Sanger sequencing. Twenty-four patients were included in transcriptomic profiling with Ampliseq Transcriptome Human Gene Expression Core Panel. The entire patients group was included in qRT-PCR analysis of selected genes expression. Immunohistochemistry was used for visualization of selected protein.

RESULTS

We found USP8 mutation in 15 patients with CD and 4 SCAs. USP8 mutations determine molecular profile of the tumours as showed by hierarchical clustering and identification of 1648 genes differentially expressed in USP8-mutated and USP8-wild-type tumours. Mutations affect many molecular pathways as observed in Gene Set Enrichment analysis. USP8-mutated adenomas showed higher level of POMC, CDC25A, MAPK4 but lower level of CCND2, CDK6, CDKN1B than USP8-wt tumours. Eighty-seven genes differentially expressed between CD-related adenomas and SCAs were found, including those involved in cell signalling (GLI2, DLC1, TBX2, RASSF6), cell adhesion (GJA1, CDH6), ion transport (KCNN4, KCNJ5) and GABA signalling (GABBR2, GABRD).

CONCLUSION

USP8 mutations occur in functioning and silent corticotrophinomas. They have pleiotropic effect, not limited to EGFR signalling, and affect expression levels of many genes involved in different pathways. Expression of GABA-related genes GABBR2, GNAL, GABARD and KCNJ5 correspond to functional status of the tumours.

Somatic mutation profiling of vulvar cancer: Exploring therapeutic targets

BACKGROUND

Vulvar squamous cell carcinoma (VSCC) constitutes over 90% of vulvar cancer. Its pathogenesis can follow two different pathways; high risk human papillomavirus (hrHPV)-dependent and HPV-independent. Due to the rarity of VSCC, molecular mechanisms underlying VSCC development remain largely unknown. The study aimed to identify pathogenic mutations implicated in the two pathways of VSCC development.

METHODS

Using next generation sequencing, 81 VSCC tumors, 52 hrHPV(+) and 29 hrHPV(-), were screened for hotspot mutations in 50 genes covered by the Ion AmpliSeq Cancer Hotspot Panel v2 Kit (Thermo Fisher Scientific).

RESULTS

Mutations of TP53 (46% and 41%, of hrHPV(+) and hrHPV(-) cases respectively) and CDKN2A (p16) (25% and 21%, of hrHPV(+) and hrHPV(-) cases respectively) were the most common genetic alterations identified in VSCC tumors. Further mutations were identified in PIK3CA, FBXW7, HRAS, FGFR3, STK11, AKT1, SMAD4, FLT3, JAK3, GNAQ, and PTEN, albeit at low frequencies. Some of the identified mutations may activate the PI3K/AKT/mTOR pathway. The activation of mTOR was confirmed in the vast majority of VSCC samples by immunohistochemical staining.

CONCLUSIONS

Detecting pathogenic mutations in 13/50 genes examined at comparable frequencies in hrHPV(+) and hrHPV(-) tumors suggest that genetic mechanisms of the two routes of VSCC pathogenesis may be similar, despite being initiated from different premalignant lesions. Importantly, our data provide a rationale for new anti-VSCC therapies targeting the PI3K/AKT/mTOR pathway.

HER2 status in breast cancer determined by IHC and FISH: comparison of the results

HER2 (human epidermal growth factor receptor 2) status became an important prognostic and predictive factor in breast carcinoma clinical management. There are two main techniques of evaluation of HER2 status: immunohistochemistry (IHC) for the protein expression and fluorescence in situ hybridization (FISH) for amplification of HER2 gene. The aim of the study was to compare the results obtained by IHC and FISH methods in determination of HER2 status in breast cancer. Three hundred and sixty breast cancer specimens were examined. Patients were operated in the Oncology Centre in Warsaw. IHC and FISH were performed in every case. IHC was performed with DAKO HercepTest and FISH with Oncor-QBiogene reagents. IHC results were classed into 4 groups, accordingly to the four-tier DAKO criteria system (0, 1+, 2+, 3+). FISH results were divided into three main categories: NA--no amplification, LA--low amplification and HA--high amplification. The number of copies of chromosome 17 was also assessed. Over 90% of cases described by IHC as 3+ exhibited amplification of HER2/neu gene. Remaining cases were positive with IHC, but presented no gene amplification. This might be due to the subjective assessment of the membrane staining. Another possibility is that overexpression of the protein was caused by mRNA stability or disorders in receptor degradation. The majority of cases classed by IHC as 2+ were also negative by FISH (80%). One fifth of IHC 2+ tumours were found to exhibit gene amplification. Remaining cases showed no amplification of HER2/neu gene, combined with aneuploidy of chromosome 17. All cases described by IHC as 0/1+ were also HER2-negative by FISH. IHC is well-established method of assessing HER2 status in breast cancer. Nonetheless, a group of cases described as 2+ should be additionally examined using FISH. The results obtained by the latter method are more reliable. In order to improve accuracy and gain the highest quality of HER2 status evaluation, in 2+ cases both methods should be applied.