Targeted STAT3 disruption in myeloid cells alters immunosuppressor cell abundance in a murine model of spontaneous medulloblastoma.
Although the immune system may provide early protection against cancer, tumors may exploit the healing arm of the immune system to enhance their growth and metastasis. For example, myeloid derived suppressor cells (MDSCs) are thought to promote tumor growth by several mechanisms, including the suppression of T cell activity. It has been suggested that STAT3 activation in myeloid cells modulates multiple aspects of MDSC physiology, including their expansion and activity. Whereas most animal studies investigating tumor immunology have used tumor implants, we used transgenic mice (Smo*) that spontaneously develop medulloblastoma brain tumors to investigate the temporal accumulation of MDSCs within tumors and how myeloid STAT3 disruption affects MDSC and other immune cell types. We found distinct populations of MDSC in medulloblastoma tumors, with a high prevalence of CD11b(+)Ly6G(+)Ly6C(low/-) cells, described previously by others as G-MDSCs. These were found early in tumor development, in premalignant lesions located on the surface of the cerebellum of 28-day-old mice. In fully developed tumors, pSTAT3 was found in the majority of these cells. Conditional STAT3 gene disruption in myeloid cells resulted in an enhanced proinflammatory phenotype of macrophages in Smo* mice. Moreover, a significant reduction in the abundance of G-MDSCs and Tregs was observed within tumors along with an increased presence of CD4(+) and CD8(+) cells. Despite these alterations in immune cells induced by myeloid STAT3 disruption, we found no effect on tumor incidence in Smo* mice with this deletion.
1.David Geffen School of Medicine, UCLA, 635 Charles E. Young Dr., South, NRB 345, Los Angeles, CA 90095-7332, USA. JWaschek@mednet.ucla.edu.
Catalina
C
Abad
Hiroko
H
Nobuta
Jiaxi
J
Li
Atsushi
A
Kasai
William H
WH
Yong
James A
JA
Waschek
D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D017353:Gene Deletion; D018390:Gene Targeting; D007108:Immune Tolerance; D007249:Inflammation / Q000276:immunology / Q000473:pathology; D008297:Male; D008527:Medulloblastoma / Q000098:blood supply / Q000276:immunology* / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000378:metabolism* / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000473:pathology; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology; D000072086:Smoothened Receptor; D050378:T-Lymphocytes, Regulatory / Q000276:immunology
D043562:Receptors, G-Protein-Coupled; D050796:STAT3 Transcription Factor; C491022:Smo protein, mouse; D000072086:Smoothened Receptor; C494087:Stat3 protein, mouse
STAT3; immunosuppression; myeloid-derived suppressor cell