BackgroundGenetic polymorphisms within the glutathione S-transferase P1 (GSTP1) gene affect the elimination of toxic xenobiotics by the GSTP1 enzyme. In dogs, exposure to environmental chemicals that may be GSTP1 substrates is associated with cancer. The objectives of this study were to investigate the genetic variability in the GSTP1 promoter in a diverse population of 278 purebred dogs, compare the incidence of any variants found between breeds, and predict their effects on gene expression. To provide information on ancestral alleles, a number of wolves, coyotes, and foxes were also sequenced.ResultsFifteen single nucleotide polymorphisms (SNPs) and two microsatellites were discovered. Three of these loci were only polymorphic in dogs while three other SNPs were unique to wolves and coyotes. The major allele at c.-46 is T in dogs but is C in the wild canids. The c.-185 delT variant was unique to dogs. The microsatellite located in the 5′ untranslated region (5′UTR) was a highly polymorphic GCC tandem repeat, consisting of simple and compound alleles that varied in size from 10 to 22-repeat units. The most common alleles consisted of 11, 16, and 17-repeats. The 11-repeat allele was found in 10% of dogs but not in the other canids. Unequal recombination and replication slippage between similar and distinct alleles may be the mechanism for the multiple microsatellites observed. Twenty-eight haplotypes were constructed in the dog, and an additional 8 were observed in wolves and coyotes. While the most common haplotype acrossbreeds was the wild-type *1A(17), other prevalent haplotypes included *3A(11) in Greyhounds, *6A(16) in Labrador Retrievers, *9A(16) in Golden Retrievers, and *8A(19) in Standard Poodles. Boxers and Siberian Huskies exhibited minimal haplotypic diversity. Compared to the simple 16*1 allele, the compound 16*2 allele (found in 12% of dogs) may interfere with transcription factor binding and/or the stability of the GSTP1 transcript.ConclusionsDogs and other canids exhibit extensive variation in the GSTP1 promoter. Genetic polymorphisms within distinct haplotypes prevalent in certain breeds can affect GSTP1 expression and carcinogen detoxification, and thus may be useful as genetic markers for cancer in dogs.Electronic supplementary materialThe online version of this article (10.1186/s40575-017-0050-8) contains supplementary material, which is available to authorized users.
The identification of novel therapies, new strategies for combination of therapies, and repurposing of drugs approved for other indications are all important for continued progress in the fight against lung cancers. Antibodies that target immune checkpoints can unmask an immunologically hot tumor from the immune system of a patient. However, despite accounts of significant tumor regression resulting from these medications, most patients do not respond. In this study, we sought to use protein expression and RNA sequencing data from The Cancer Genome Atlas and two smaller studies deposited onto the Gene Expression Omnibus (GEO) to advance our hypothesis that inhibition of SHP-2, a tyrosine phosphatase, will improve the activity of immune checkpoint inhibitors (ICI) that target PD-1 or PD-L1 in lung cancers. We first collected protein expression data from The Cancer Proteome Atlas (TCPA) to study the association of SHP-2 and PD-L1 expression in lung adenocarcinomas. RNA sequencing data was collected from the same subjects through the NCI Genetic Data Commons and evaluated for expression of the PTPN11 (SHP-2) and CD274 (PD-L1) genes. We then analyzed RNA sequencing data from a series of melanoma patients who were either treatment naïve or resistant to ICI therapy. PTPN11 and CD274 expression was compared between groups. Finally, we analyzed gene expression and drug response data collected from 21 non-small cell lung cancer (NSCLC) patients for PTPN11 and CD274 expression. From the three studies, we hypothesize that the activity of SHP-2, rather than the expression, likely controls the expression of PD-L1 as only a weak relationship between PTPN11 and CD274 expression in either lung adenocarcinomas or melanomas was observed. Lastly, the expression of CD274, not PTPN11, correlates with response to ICI in NSCLC.
Immune checkpoint inhibitors (ICIs), specifically those which target the T-cell surface receptor Programmed Cell Death-1 (PD-1) and its ligand, Programmed cell death ligand-1 (PD-L1), have demonstrated substantial clinical benefit in patients with non-small cell lung cancer (NSCLC). Tumoral PD-L1 expression may be important for response to therapy, but the precise mechanism of regulation has yet to be fully elucidated. It is known that PD-L1 expression is elevated in cancers harboring mutations in the RAS family of genes, specifically KRAS. Mutations in the KRAS gene are found in up to 30% of NSCLC tumors, and there are no targeted treatment options available for this subset of patients. The tyrosine phosphatase, SHP-2, has been shown to be a critical regulator of the KRAS signaling cascade. Therefore, genes regulated by the RAS/MAPK signaling cascade, including PD-L1, may be modulated by SHP-2 inhibition. Thus, this study aims to investigate the impact of SHP-2 activity on PD-L1 expression in NSCLC. The allosteric inhibitor of SHP-2, SHP099, was used to ablate SHP-2 activity in KRAS-mutant NSCLC cell lines, H460, A549, H2122, and EGFR-mutant NSCLC cell line PC9. PD-L1 levels were quantified by western blot and flow cytometry analyses. PD-L1 mRNA was measured by quantitative real time PCR (qRT-PCR) analysis. SHP099 activity was confirmed by SHP-2, siRNA transfection in KRAS active cell lines. Inhibition of SHP-2 led to increased levels of PD-L1 expression in the KRAS-mutant cell lines, but not in the EGFR-mutant cells. Analysis of PD-L1 surface expression by flow cytometry confirmed that surface PD-L1 levels increased following exposure to SHP099. To determine whether SHP-2 controlled expression at the transcriptional level, mRNA quantification by qRT-PCR displayed increased levels of PD-L1 mRNA following SHP099 treatment. Together, these results suggest that SHP-2 regulates PD-L1 expression in KRAS-active NSCLC at the level of PD-L1 gene expression. It is presently unclear whether SHP-2 also has a role in controlling protein turnover. Using SHP-2 mutant constructs that mimic a constitutively active phosphatase, we hope to gain further insight into the roles of both SHP-2 catalytic and scaffolding functionality on PD-L1 expression. Citation Format: Keller Toral. The tyrosine phosphatase, SHP-2, is involved in regulating PD-L1 expression in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1773.
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