Inhibition of protein phosphatase 2A (PP2A) activity has been identified as a prerequisite for the transformation of human cells. However, the molecular mechanisms by which PP2A activity is inhibited in human cancers are currently unclear. In this study, we describe a cellular inhibitor of PP2A with oncogenic activity. The protein, designated Cancerous Inhibitor of PP2A (CIP2A), interacts directly with the oncogenic transcription factor c-Myc, inhibits PP2A activity toward c-Myc serine 62 (S62), and thereby prevents c-Myc proteolytic degradation. In addition to its function in c-Myc stabilization, CIP2A promotes anchorage-independent cell growth and in vivo tumor formation. The oncogenic activity of CIP2A is demonstrated by transformation of human cells by overexpression of CIP2A. Importantly, CIP2A is overexpressed in two common human malignancies, head and neck squamous cell carcinoma (HNSCC) and colon cancer. Thus, our data show that CIP2A is a human oncoprotein that inhibits PP2A and stabilizes c-Myc in human malignancies.

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Degradation of extracellular matrix is crucial for malignant tumor growth, invasion, metastasis and angiogenesis. Matrix metalloproteinases (MMPs) are a family of zinc-dependent neutral endopeptidases collectively capable of degrading essentially all matrix components. Elevated levels of distinct MMPs can be detected in tumor tissue or serum of patients with advanced cancer, and their role as prognostic indicators in cancer has been widely examined. In addition, therapeutic intervention in tumor growth and invasion based on inhibition of MMP activity is under intensive investigation and several MMP inhibitors (MMPIs) are in clinical cancer trials. Even though results of the first clinical trials in advanced cancer have been mostly disappointing, there are also positive results. Recent observations show, that certain MMPs limit tumor growth. Therefore, identification of proper MMPs for therapeutic intervention with array-based molecular classifications of tumors and targeting these with more specific MMPIs in combination with conventional chemotherapy is expected to provide a feasible approach for cancer therapy. MMPIs represent a totally different therapeutic modality from proven anti-cancer drugs and thus traditional approaches to evaluate drug efficiency cannot be used without modification. In this review, we discuss the current view on the feasibility of MMPs as targets for therapeutic intervention in cancer.

Recent studies indicate that the specificity of p38 mitogenactivated protein kinase (MAPK)-mediated cellular stress responses is determined by the expression pattern of the distinct p38 isoforms. Here, we have analysed the function of distinct p38 isoforms in the growth and invasion of head and neck squamous cell carcinomas (HNSCCs). Activation of p38 MAPK by arsenite resulted in inactivation of the ERK1,2 signaling pathway by dephosphorylation of MEK1,2 in primary human epidermal keratinocytes (HEKs), whereas in HNSCC cells this p38-mediated inhibition of the ERK1,2 pathway was absent. Quantitation of p38 pathway component mRNA expression in HNSCC cell lines (n ¼ 42) compared to HEKs (n ¼ 8) revealed that p38a and p38d isoforms are predominantly expressed in both cell types and that MKK3 is the primary upstream activator expressed. Inhibition of endogenous p38a or p38d activity by adenoviral delivery of corresponding dominant-negative p38 isoforms potently reduced MMP-13 and MMP-1 expressions, and suppressed the invasion of HNSCC cells through collagen. Dominantnegative p38a and p38d inhibited squamous cell carcinoma (SCC) cell proliferation and inhibition of p38a activity also compromised survival of SCC cells. p38a and p38d were predominantly expressed in HNSCCs (n ¼ 24) and nonneoplastic epithelium in vivo (n ¼ 6), with MKK3 being the primary upstream activator. Activation and expression of p38a and p38d by tumor cells was detected in HNSCCs in vivo (n ¼ 16). Adenoviral expression of dominantnegative p38a or p38d in cutaneous SCC cells potently inhibited their implantation in skin of severe combined immunodeficiency mice and growth of xenografts in vivo. Our results indicate that p38a and p38d specifically promote the malignant phenotype of SCC cells by regulating cell survival, proliferation and invasion, suggesting these p38 MAPK isoforms as potential therapeutic targets in HNSCCs.

The incidence of cutaneous squamous cell carcinoma (cSCC) is increasing globally. We have studied the expression of complement system components in cSCC. Expression profiling of cSCC cell lines (n=8) and normal human epidermal keratinocytes (n=5) with Affymetrix and quantitative real-time PCR (qPCR) revealed upregulation of complement factor H (CFH) and factor H-like protein-1 (FHL-1) in cSCC cell lines. The expression of CFH and FHL-1 mRNAs was also significantly higher in cSCC tumors (n=6) than in normal skin (n=11). Analysis of CFH and FHL-1 expression in vivo in invasive cSCCs (n=65), in situ cSCCs (n=38), and premalignant lesions (actinic keratoses, n=37) by immunohistochemistry showed that they were specifically expressed by tumor cells in cSCCs and the staining intensity was stronger in cSCCs than in in situ cSCCs and actinic keratoses. The expression of CFH by cSCC cells was upregulated by IFN-γ and the basal CFH and FHL-1 expression was dependent on extracellular signal-regulated kinase (ERK)1/2 and p38 signaling. Knockdown of CFH and FHL-1 expression inhibited proliferation and migration of cSCC cells and inhibited basal ERK1/2 activation. These results provide evidence for a role of CFH and FHL-1 in cSCC progression and identify them as progression markers and potential therapeutic targets in SCCs of skin.

Purpose: Head and neck squamous cell carcinomas (HNSCC) are characterized by high morbidity and mortality, largely due to the high invasive and metastatic potential of these tumors, high recurrence rates, and low treatment responses. Proteinases have been implicated in several aspects of tumor growth and metastasis in a broad range of tumors including HNSCC.Experimental Design: Comprehensive expression profiling of proteinases [matrix metalloproteinases (MMPs), A disintegrin and metalloproteinase (ADAMs), and ADAMs with thrombospondin motif (ADAMTSs)] and their inhibitors [tissue inhibitor of metalloproteinases (TIMPs)] was done using quantitative real-time reverse transcription-PCR analysis of a large cohort of tissue samples representing the tumor (n = 83), the invasive margin (n = 41), and the adjacent tissue (n = 41) from 83 HNSCC patients, along with normal tissue controls (n = 13), as well as cell lines established from tumors of 34 HNSCC patients.Results: The results show specifically elevated gene expression of several proteinases, including MMP1, MMP3, MMP10, and MMP13 within tumor tissue and peritumoral adjacent tissue. In addition, the results identify several novel HNSCC-associated proteinases, including ADAM8, ADAM9, ADAM17, ADAM28, ADAMTS1, ADAMTS8, and ADAMTS15. There were also significant differences in proteinase expression based on clinical parameters, i.e., tumor location, grade, and local invasion. MMP13 expression was significantly higher in large (>4 cm) locally invasive tumors (P < 0.05). MMP9 expression was significantly decreased in tumors with regional metastasis, whereas increased expression of ADAM8 was noted in the metastatic tumors (P < 0.001 for both).Conclusions: These findings suggest the HNSCC degradome as a valuable source of diagnostic, predictive, and prognostic molecular markers for these malignant tumors. Clin Cancer Res; 16(7); 2022-35. ©2010 AACR.Head and neck squamous cell carcinoma (HNSCC) can be defined as a malignant tumor derived from the squamous epithelial cells that line the upper aerodigestive tract, which extends from the surface of the lips to the cervical surface of the esophagus. HNSCC is the fifth most common cancer worldwide and, in 2002, was the cause of over 300,000 deaths worldwide (1). The overall survival rates of HNSCC patients (∼50%) have remained unaltered for over 20 years. The presence of lymph node metastases is the single most important predictive factor for HNSCC patients resulting in a 50% decrease in survival (2, 3).The degradome comprises both the complete set of proteases (also known as peptidases and proteinases) expressed by a cell, tissue, or organism at a given time, and the substrate repertoire of a given proteinase (4). There is a well-established association between matrix proteolysis and cancer invasion and metastasis, and the proteinases of every class have been linked to malignancy and invasion of tumor cells (5). However, through the study of transgenic models and the identification of further proteinases and proteinase s...

Summary Co-expression of several members of the matrix metalloproteinase (MMP) family is characteristic of human malignant tumours. To investigate the role of stromelysin-2 (MMP-10) in growth and invasion of skin tumours, we studied cutaneous carcinomas with high metastatic capacity (squamous cell carcinomas, SCCs), only locally destructive tumours (basal cell carcinomas, BCCs) and pre-malignant lesions (Bowen's disease and actinic keratosis) using in situ hybridization. Expression of MMP-10 was compared with that of stromelysin-1 (MMP-3) and of MT1-MMP, the expression of which has been shown to correlate with tumour invasiveness. MMP-10 was expressed in 13/21 SSCs and 11/19 BCCs only in epithelial laminin-5 positive cancer cells, while premalignant lesions were entirely negative. MT1-MMP mRNA was detected in 19/21 SCCs both in epithelial cancer cells and stromal fibroblasts and in 14/18 BCCs only in fibroblasts. The level of MMP-10 was upregulated in a cutaneous SCC cell line (UT-SCC-7) by transforming growth factor-α and keratinocyte growth factor, and by interferon-γ in combination with transforming growth factor-β1 and tumour necrosis factor-α both in UT-SCC-7 and HaCaT cells. Our results show that MMP-10 expression does not correlate with the invasive behaviour of tumours as assessed by their histology and MT1-MMP expression, but may be induced by the wound healing and inflammatory matrix remodelling events associated with skin tumours.

The incidence of cutaneous squamous cell carcinoma (cSCC) is rising worldwide. We have examined the role of complement components in the progression of cSCC. Analysis of cSCC cell lines (n=8) and normal human epidermal keratinocytes (n=11) with whole transcriptome profiling (SOLiD), quantitative real-time reverse transcriptase-PCR, and western blotting revealed marked overexpression of complement factor I (CFI) in cSCC cells. Immunohistochemical analysis for CFI in vivo showed stronger tumor cell-specific labeling intensity in invasive sporadic cSCCs (n=83) and recessive dystrophic epidermolysis bullosa-associated cSCCs (n=7) than in cSCC in situ (n=65), premalignant epidermal lesions (actinic keratoses, n=64), benign epidermal papillomas (seborrheic keratoses, n=39), and normal skin (n=9). The expression of CFI was higher in the aggressive Ha-ras-transformed cell line (RT3) than in less tumorigenic HaCaT cell lines (HaCaT, A5, and II-4). The expression of CFI by cSCC cells was upregulated by IFN-γ and IL-1β. Knockdown of CFI expression inhibited proliferation and migration of cSCC cells and resulted in inhibition of basal extracellular signal-regulated kinase (ERK) 1/2 activation. Knockdown of CFI expression potently inhibited growth of human cSCC xenograft tumors in vivo. These results provide evidence for the role of CFI in the progression of cSCC and identify it as a potential therapeutic target in this nonmelanoma skin cancer.