PDGFRβ promotes oncogenic progression via STAT3/STAT5 hyperactivation in anaplastic large cell lymphoma

BACKGROUND

Anaplastic large cell lymphoma (ALCL) is an aggressive non-Hodgkin T cell lymphoma commonly driven by NPM-ALK. AP-1 transcription factors, cJUN and JUNb, act as downstream effectors of NPM-ALK and transcriptionally regulate PDGFRβ. Blocking PDGFRβ kinase activity with imatinib effectively reduces tumor burden and prolongs survival, although the downstream molecular mechanisms remain elusive.

METHODS AND RESULTS

In a transgenic mouse model that mimics PDGFRβ-driven human ALCL in vivo, we identify PDGFRβ as a driver of aggressive tumor growth. Mechanistically, PDGFRβ induces the pro-survival factor Bcl-xL and the growth-enhancing cytokine IL-10 via STAT5 activation. CRISPR/Cas9 deletion of both STAT5 gene products, STAT5A and STAT5B, results in the significant impairment of cell viability compared to deletion of STAT5A, STAT5B or STAT3 alone. Moreover, combined blockade of STAT3/5 activity with a selective SH2 domain inhibitor, AC-4-130, effectively obstructs tumor development in vivo.

CONCLUSIONS

We therefore propose PDGFRβ as a novel biomarker and introduce PDGFRβ-STAT3/5 signaling as an important axis in aggressive ALCL. Furthermore, we suggest that inhibition of PDGFRβ or STAT3/5 improve existing therapies for both previously untreated and relapsed/refractory ALK+ ALCL patients.

Stat5 gene dosage in T cells modulates CD8+ T-cell homeostasis and attenuates contact hypersensitivity response in mice

BACKGROUND

Contact hypersensitivity assay (CHS) faithfully models human allergies. The Stat5 transcription factors are essential for both lymphocyte development and acute immune responses. Although consequences of Stat5 ablation and transgenic overexpression for the lymphocyte development and functions have been extensively studied, the role of Stat5 gene dosage in contact allergies has not been addressed.

OBJECTIVE

We investigated the effect of Stat5 gene dosage modulation in contact allergies using CHS in mice.

METHODS

Transgenic animals heterozygous for the germline Stat5 null allele were subjected to CHS. To dissect cell type sensitive to Stat5 gene dosage, animals with Stat5 haplo-insufficiency in T cells, where one Stat5 allele was removed by Lck-Cre-mediated deletion (Stat5(ΔT/+)), were tested by CHS. Frequency of T cells, B cells, and monocytes were analyzed in Stat5(ΔT/+) and wild-type animals by flow cytometry. Proliferation of Stat5(ΔT/+) CD8(+) T cells was studied in vitro by stimulation with IL-4 and IL-2 cytokines, and changes in the expression of Stat5 target genes were assayed by quantitative real-time PCR assay.

RESULT

Haplo-insufficiency of Stat5 in T cells leads to the reduction in CD8(+) T cells in all lymphoid organs and attenuates CHS response. Stat5(ΔT/+) CD8(+) T cells failed to fully activate Stat5-dependent expression of cell cycle/survival target genes, such as Bcl2 and Pim1, and to proliferate efficiently in response to IL-2 and IL-4 cytokine.

CONCLUSION

Our data identify Stat5 as a dose-dependent regulator of CD8(+) T-cell functions in contact allergies and suggest that modulation of Stat5 dosage could be used to target contact allergies in humans.

Osteopontin deficiency protects against obesity-induced hepatic steatosis and attenuates glucose production in mice

AIMS/HYPOTHESIS

Obesity is strongly associated with the development of non-alcoholic fatty liver disease (NAFLD). The cytokine osteopontin (OPN) was recently shown to be involved in obesity-induced adipose tissue inflammation and reduced insulin response. Accumulating evidence links OPN to the pathogenesis of NAFLD. Here we aimed to identify the role of OPN in obesity-associated hepatic steatosis and impaired hepatic glucose metabolism.

METHODS

Wild-type (WT) and Opn (also known as Spp1) knockout (Opn (-/-)) mice were fed a high-fat or low-fat diet to study OPN effects in obesity-driven hepatic alterations.

RESULTS

We show that genetic OPN deficiency protected from obesity-induced hepatic steatosis, at least in part, by downregulating hepatic triacylglycerol synthesis. Conversely, absence of OPN promoted fat storage in adipose tissue thereby preventing the obesity-induced shift to ectopic fat accumulation in the liver. Euglycaemic-hyperinsulinaemic clamp studies revealed that insulin resistance and excess hepatic glucose production in obesity were significantly attenuated in Opn (-/-) mice. OPN deficiency markedly improved hepatic insulin signalling as shown by enhanced insulin receptor substrate-2 phosphorylation and prevented upregulation of the major hepatic transcription factor Forkhead box O1 and its gluconeogenic target genes. In addition, obesity-driven hepatic inflammation and macrophage accumulation was blocked by OPN deficiency.

CONCLUSIONS/INTERPRETATION

Our data strongly emphasise OPN as mediator of obesity-associated hepatic alterations including steatosis, inflammation, insulin resistance and excess gluconeogenesis. Targeting OPN action could therefore provide a novel therapeutic strategy to prevent obesity-related complications such as NAFLD and type 2 diabetes.