Re-expression of epigenetically silenced PTPRR by histone acetylation sensitizes RAS-mutant lung adenocarcinoma to SHP2 inhibition

Silenced protein tyrosine phosphatase receptor type R (PTPRR) participates in mitogen-activated protein kinase (MAPK) signaling cascades during the genesis and development of tumors. Rat sarcoma virus (Ras) genes are frequently mutated in lung adenocarcinoma, thereby resulting in hyperactivation of downstream MAPK signaling. However, the molecular mechanism manipulating the regulation and function of PTPRR in RAS-mutant lung adenocarcinoma is not known. Patient records collected from the Cancer Genome Atlas and Gene Expression Omnibus showed that silenced PTPRR was positively correlated with the prognosis. Exogenous expression of PTPRR suppressed the proliferation and migration of lung cancer cells. PTPRR expression and Src homology 2 containing protein tyrosine phosphatase 2 (SHP2) inhibition acted synergistically to control ERK1/2 phosphorylation in RAS-driven lung cancer cells. Chromatin immunoprecipitation assay revealed that HDAC inhibition induced enriched histone acetylation in the promoter region of PTPRR and recovered PTPRR transcription. The combination of the HDAC inhibitor SAHA and SHP2 inhibitor SHP099 suppressed the progression of lung cancer markedly in vitro and in vivo. Therefore, we revealed the epigenetic silencing mechanism of PTPRR and demonstrated that combination therapy targeting HDAC and SHP2 might represent a novel strategy to treat RAS-mutant lung cancer.

Genetic ablation of phosphatidylcholine transfer protein/StarD2 in ob/ob mice improves glucose tolerance without increasing energy expenditure

OBJECTIVE

Phosphatidylcholine transfer protein (PC-TP; synonym StarD2) is highly expressed in liver and oxidative tissues. PC-TP promotes hepatic glucose production during fasting and aggravates glucose intolerance in high fat fed mice. However, because PC-TP also suppresses thermogenesis in brown adipose tissue (BAT), its direct contribution to obesity-associated diabetes in mice remains unclear. Here we examined the effects of genetic PC-TP ablation on glucose homeostasis in leptin-deficient ob/ob mice, which exhibit both diabetes and altered thermoregulation.

ANIMALS/METHODS

Mice lacking both PC-TP and leptin (Pctp^-/-;ob/ob) were prepared by crossing Pctp^-/- with ob/+ mice. Glucose homeostasis was assessed by standard assays, and energy expenditure was determined by indirect calorimetry using a comprehensive laboratory animal monitoring system, which also recorded physical activity and food intake. Body composition was determined by NMR and hepatic lipids by enzymatic assays. Core body temperature was measured using a rectal thermocouple probe.

RESULTS

Pctp^-/-;ob/ob mice demonstrated improved glucose homeostasis, as evidenced by markedly improved glucose and pyruvate tolerance tests, without changes in insulin tolerance. However, there were no differences in EE at any ambient temperature. There were also no effects of PC-TP expression on physical activity, food intake or core body temperature.

CONCLUSIONS

Improved glucose tolerance in Pctp^-/-;ob/ob mice in the absence of increases in energy expenditure or core body temperature indicates a direct pathogenic role for PC-TP in diabetes in leptin deficient mice.

Androgen-regulation of the protein tyrosine phosphatase PTPRR activates ERK1/2 signalling in prostate cancer cells

BACKGROUND

Androgens drive the onset and progression of prostate cancer (PCa) via androgen receptor (AR) signalling. The principal treatment for PCa is androgen deprivation therapy, although the majority of patients eventually develop a lethal castrate-resistant form of the disease, where despite low serum testosterone levels AR signalling persists. Advanced PCa often has hyper-activated RAS/ERK1/2 signalling thought to be due to loss of function of key negative regulators of the pathway, the details of which are not fully understood.

METHODS

We recently carried out a genome-wide study and identified a subset of 226 novel androgen-regulated genes (PLOS ONE 6:e29088, 2011). In this study we have meta-analysed this dataset with genes and pathways frequently mutated in PCa to identify androgen-responsive regulators of the RAS/ERK1/2 pathway.

RESULTS

We find the PTGER4 and TSPYL2 genes are up-regulated by androgen stimulation and the ADCY1, OPKR1, TRIB1, SPRY1 and PTPRR are down-regulated by androgens. Further characterisation of PTPRR protein in LNCaP cells revealed it is an early and direct target of the androgen receptor which negatively regulates the RAS/ERK1/2 pathway and reduces cell proliferation in response to androgens.

CONCLUSION

Our data suggest that loss of PTPRR in clinical PCa is one factor that might contribute to activation of the RAS/ERK1/2 pathway.

Epigenetic silencing of PTPRR activates MAPK signaling, promotes metastasis and serves as a biomarker of invasive cervical cancer

Epigenetic modifications are a driving force in carcinogenesis. However, their role in cancer metastasis remains poorly understood. The present study investigated the role of DNA methylation in the cervical cancer metastasis. Here, we report evidence of the overexpression of DNA methyltransferases 3B (DNMT3B) in invasive cervical cancer and of the inhibition of metastasis by DNMT3B interference. Using methyl-DNA immunoprecipitation coupled with microarray analysis, we found that the protein tyrosine phosphatase receptor type R (PTPRR) was silenced through DNMT3B-mediated methylation in the cervical cancer. PTPRR inhibited p44/42 MAPK signaling, the expression of the transcription factor AP1, human papillomavirus (HPV) oncogenes E6/E7 and DNMTs. The methylation status of PTPRR increased in cervical scrapings (n=358) in accordance with disease severity, especially in invasive cancer. Methylation of the PTPRR promoter has an important role in the metastasis and may be a biomarker of invasive cervical cancer.

[Association between protein tyrosine phosphatase receptor type R gene and major depressive disorder]

OBJECTIVE

To explore the genetic association between protein tyrosine phosphatase receptor type R (PTPRR) gene polymorphism and major depressive disorder (MDD) and its endophenotype.

METHODS

A total of 517 unrelated MDD patients and 455 unrelated healthy subjects were recruited in this study to detect 11 single nucleotide polymorphisms (SNPs) in the PTPRR locus. They all were of the Chinese Han origin. Genotyping of SNPs was performed by matrix assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) -based genotyping approach. The UNPHASED program was applied to analyze the genotyping data.

RESULTS

Of the 11 selected SNPs, no significant allelic and genotypic association was found between MDD patients and the normal controls (corrected P > 0.05). However, analysis of haplotypes showed that the three SNPs haplotype rs1398599 (C) -rs2175711 (A) - rs4489789 (T) (P = 0.0023, OR = 1.334, 95% CI = 1.104-1.612) and four SNPs haplotype rs11178391 (C) -rs1398599 (C) -rs2175711 (A)-rs4489789(T) (P = 0.0063, OR = 1.281, 95% CI = 1.059-1.549) were associated with increased risk of MDD. Quantitative trait analysis revealed that rs2203231 in the PTPRR locus had strong allelic and genotypic association with the raw score of long-term memory (P = 0.0038 for allelic association, P = 0.0024 for genotypic association), the scaled score of long-term memory (P = 0.0057 for allelic association, P = 0.0038 for genotypic association), the raw score of short-term memory (P = 0.0027 for allelic association, P = 0.0015 for genotypic association), and the scaled score of short-term memory (P = 0.0035 for allelic association, P = 0.002 for genotypic association) in MDD patients.

CONCLUSION

The polymorphism of PTPRR gene rs2203231 may be associated with the impairment of long-term and short-term memories in MDD patients.