Dysregulation of CXCL9 and reduced tumor growth in Egr-1 deficient mice.
BACKGROUND
Early growth response-1 (Egr-1) is an immediate-early transcription factor inducible in the vasculature in response to injury, shear stress, and other stimuli. Mice lacking Egr-1 have a profound deficit in the ability to recover from femoral artery ligation, suggesting a role in neovascularization. Previous studies have shown that manipulating Egr-1 expression can have either positive or negative effects on tumor growth. We hypothesized that Egr-1 knockout mice might exhibit reduced tumor growth, possibly due to a reduced capacity to respond to angiogenic signals from a growing tumor.


RESULTS
We injected 106 Lewis lung carcinoma (LLC1) cells subcutaneously in the flank of wild type and Egr-1 knockout mice. The average mass of tumors from wild type mice at 12 days after implantation was 413 +/- 128 mg, while those from Egr-1-/- mice was 219 +/- 81 mg (p = 0.001, mean +/- SD). However, sectioning the tumors and staining with anti-CD31 antibodies revealed no difference in the vascularity of the tumors and there was no difference in angiogenic growth factor expression. Expression of the chemokine Mig (CXCL9) was increased 2.8-fold in tumors from knockout mice, but no increase was found in serum levels of Mig. Natural killer cells have a 1.7-fold greater prevalence in the CD45+ cells found in tumors from Egr-1-/- mice compared to those from wild type mice. Immunohistochemical staining suggests that Mig expression in the tumors comes from invading macrophages.


CONCLUSIONS
Mice deficient in Egr-1 exhibit reduced growth of LLC1 tumors, and this phenomenon is associated with overexpression of Mig locally within the tumor. There are no obvious differences in tumor vascularity in the knockout mice. Natural killer cells accumulate in the tumors grown in Egr-1-/- mice, providing a potential mechanism for the reduction in growth.
Caso
Giuseppe
G
Department of Surgery, Stony Brook University, Stony Brook, NY, USA.giuseppe.caso@stonybrook.edu
Barry
Catherine
C
Patejunas
Gerald
G
D000818:Animals; D018827:Carcinoma, Lewis Lung / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D054370:Chemokine CXCL9 / Q000235:genetics* / Q000378:metabolism; D051766:Early Growth Response Protein 1 / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D007694:Killer Cells, Natural / Q000378:metabolism / Q000473:pathology; D017254:Leukemic Infiltration / Q000235:genetics / Q000473:pathology; D008264:Macrophages / Q000378:metabolism / Q000473:pathology; D008546:Melanoma, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D047368:Tumor Burden / Q000235:genetics*
D054370:Chemokine CXCL9; C485969:Cxcl9 protein, mouse; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse