Tpl2 knockout keratinocytes have increased biomarkers for invasion and metastasis

Abstract

Skin cancer is the most common form of cancer in the USA, with an estimated two million cases diagnosed annually. Tumor progression locus 2 (Tpl2), also known as MAP3K8, is a serine/threonine protein kinase in the mitogen-activated protein kinase signal transduction cascade. Tpl2 was identified by our laboratory as having a tumor suppressor function in skin carcinogenesis, with the absence of this gene contributing to heightened inflammation and increased skin carcinogenesis. In this study, we used gene expression profiling to compare expression levels between Tpl2 (+/+) and Tpl2 (-) (/-) keratinocytes. We identified over 2000 genes as being differentially expressed between genotypes. Functional annotation analysis identified cancer, cell growth/proliferation, cell death, cell development, cell movement and cell signaling as the top biological processes to be differentially regulated between genotypes. Further microarray analysis identified several candidate genes, including Mmp1b, Mmp2, Mmp9 and Mmp13, involved in migration and invasion to be upregulated in Tpl2 (-) (/-) keratinocytes. Moreover, Tpl2 (-/-) keratinocytes had a significant downregulation in the matrix metalloproteinase (MMP) inhibitor Timp3. Real-time PCR validated the upregulation of the MMPs in Tpl2 (-/-) keratinocytes and zymography confirmed that MMP2 and MMP9 activity was higher in conditioned media from Tpl2 (-/-) keratinocytes. Immunohistochemistry confirmed higher MMP9 staining in 12-O-tetradecanoylphorbol-13-acetate-treated skin from Tpl2 (-/-) mice and grafted tumors formed from v-ras(Ha) retrovirus-infected Tpl2 (-/-) keratinocytes. Additionally, Tpl2 (-/-) keratinocytes had significantly higher invasion, malignant conversion rates and increased endothelial cell tube formation when compared with Tpl2 (+/+) keratinocytes. In summary, our studies reveal that keratinocytes from Tpl2 (-/-) mice demonstrate a higher potential to be invasive and metastatic.

Tumor Progression Locus 2 (Tpl2) Kinase as a Novel Therapeutic Target for Cancer: Double-Sided Effects of Tpl2 on Cancer

“…Tpl2 ablation significantly enhanced tumor initiation and progression in a chemical-induction mouse skin cancer model via up-regulated NF-κB signaling and MMP activity [ 94 , 95 , 96 ].…”

“…Mechanistically, oncogenic effects of Tpl2 ablation were mediated by increased NF-κB activity, which ultimately induced both skin tumorigenesis and inflammation [ 95 ]. Comparative gene expression profiling between Tpl2 +/+ and Tpl2 −/− mice further demonstrated that MMP1b/2/9/13 that stimulate the migration and invasion of cancer cells are up-regulated in Tpl2 −/− keratinocytes [ 96 ].…”

TPL2 kinase regulates the inflammatory milieu of the myeloma niche

“…57 To test the hypothesis that TPL2 is essential for MAM activation and myeloma progression, we crossed Tpl2 2/2 animals 41 to the genetically engineered myeloma model, Vk*MYC. 58,59 Following its initial discovery as an oncogene, 60 Tpl2 has been shown to variably act as a tumor promoter or suppressor gene in various models of solid tumors, [61][62][63][64][65][66][67][68][69][70][71] Figure 4C). By contrast, the rates of apoptosis (cleaved caspase 3 positivity) in CD138 1 cells from tumor-matched animals were low and not significantly different between the 2 genotypes ( Figure 4D).…”

Tumor progression locus 2 (TPL2) in tumor-promoting Inflammation, Tumorigenesis and Tumor Immunity

“…Contrary to the tumorigenic function of the TPL2 kinase illustrated in the above sections, TPL2 ablation is shown to increase tumorigenesis in experimental skin cancer, colitis-associated cancer (CAC) and lung cancer 41 , 89 , 101 . The increased tumorigenesis in TPL2 -/- mice is attributed to augmented inflammatory responses due to increased inflammatory cell infiltration and malignant transformation driven by exaggerated NF-κB activation 88 , 101 . The inhibition of NF-κB with SN50 was shown to suppress inflammatory cell infiltration and NF-κB activity in wild type (WT) mice and keratinocytes 88 , 102 .…”