Specific pathways linking heterotrimeric G proteins and Fcγ receptors to the actin-based cytoskeleton are poorly understood. To test a requirement for Rho family members in cytoskeletal events mediated by structurally diverse receptors in leukocytes, we transfected the full-length human chemotactic peptide receptor in RAW 264.7 cells and examined cytoskeletal alterations in response to the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP), colony stimulating factor–1 (CSF-1), IgG-coated particles, and phorbol 12-myristate 13-acetate (PMA). Expression of Rac1 N17, Cdc42 N17, or the GAP domain of n-chimaerin inhibited cytoskeletal responses to FMLP and CSF-1, and blocked phagocytosis. Accumulation of F-actin– rich “phagocytic cups” was partially inhibited by expression of Rac1 N17 or Cdc42 N17. In contrast, PMA-induced ruffling was not inhibited by expression of Rac1 N17, but was blocked by expression of Cdc42 N17, indicating that cytoskeletal inhibition by these constructs was nonoverlapping. These results demonstrate differential requirements for Rho family GTPases in leukocyte motility, and indicate that both Rac1 and Cdc42 are required for Fcγ receptor– mediated phagocytosis and for membrane ruffling mediated by structurally distinct receptors in macrophages.

Interactions between the p53 and PI3K/AKT pathways play a significant role in the determination of cell death/survival. In benign cells these pathways are interrelated through the transcriptional regulation of PTEN by p53, which is required for p53-mediated apoptosis. PTEN exerts its effects by decreasing the phosphorylated AKT fraction, thereby diminishing prosurvival activities. However, the link between these pathways in cancer is not known. In this study, PIK3CA, encoding the p110␣ catalytic subunit of PI3K, is identified as an oncogene involved in upper aerodigestive tract (UADT) carcinomas. Simultaneous abnormalities in both pathways are rare in primary tumors, suggesting that amplification of PIK3CA and mutation of p53 are mutually exclusive events and either event is able to promote a malignant phenotype. Moreover, the negative effect of p53 induction on cell survival involves the transcriptional inhibition of PIK3CA that is independent of PTEN activity, as PTEN is not expressed in the primary tumors. Conversely, constitutive activation of PIK3CA results in resistance to p53-related apoptosis in PTEN deficient cells. Thus, p53 regulates cell survival by inhibiting the PI3K/AKT prosurvival signal independent of PTEN in epithelial tumors. This inhibition is required for p53-mediated apoptosis in malignant cells.

Chromosomal amplification at 3q is common to multiple human cancers, but has a specific predilection for squamous cell carcinomas (SCC) of mucosal origin. We identified and characterized a novel oncogene, SCC-related oncogene (SCCRO), which is amplified along the 3q26.3 region in human SCC. Amplification and overexpression of SCCRO in these tumors correlate with poor clinical outcome. The importance of SCCRO amplification in malignant transformation is established by the apoptotic response to short hairpin RNA against SCCRO, exclusively in cancer cell lines carrying SCCRO amplification. The oncogenic potential of SCCRO is underscored by its ability to transform fibroblasts (NIH-3T3 cells) in vitro and in vivo. We show that SCCRO regulates Gli1-a key regulator of the hedgehog (HH) pathway. Collectively, these data suggest that SCCRO is a novel component of the HH signaling pathway involved in the malignant transformation of squamous cell lineage.

VEGF-A expression correlates with SCCRO expression in these primary human lung squamous cell carcinomas and is a predictor of clinical behavior. This data supports the association of SCRRO and VEGF-A in the induction of angiogenesis.

Purpose: Ectopic expression of squamous cell carcinoma^related oncogene (SCCRO or DCUN1D1) in NIH-3T3 cells induces invasion in vitro and produces highly invasive xenografts in nude mice with a propensity for regional lymphatical metastasis. The aim of this study was to identify the molecular mechanism underlying SCCRO-induced invasion and metastasis. Experimental Design: The molecular mechanism of SCCRO-mediated effects on matrix metalloproteinase-2 (MMP2) levels and activity were assessed using a combination of cell biological and molecular methods, including real-time PCR, reporter assay, RNA interference, and chromatin immunoprecipitation assay. Tumor specimens from primary upper aerodigestive tract carcinomas (n = 89) were examined for levels of SCCRO, MMP2, MMP9, MT1-MMP, TIMP1, andTIMP2 mRNA by real-time PCR. Results: Overexpression of SCCRO increases MMP2 levels and activity, which is required for SCCRO-induced invasion. Modified McKay assays reveal that SCCRO does not bind to the MMP2 promoter, suggesting that its transcriptional effects are indirect. Deletion or mutation of the activator protein-2 (AP2) and p53 binding element within the MMP2 promoter abrogates SCCRO-driven activation. Ectopic expression of SCCRO increases AP2 levels and promotes the binding of p53 to the MMP2 promoter. Consistent with these findings, SCCRO and MMP2 are coexpressed (P < 0.0001; r 2 = 0.58; 95% confidence interval, 0.46-0.69) in primary (upper aerodigestive tract) carcinomas (n = 89), and this coexpression is associated with an increased prevalence of regional nodal metastasis (P = 0.04; relative risk, 1.53). Conclusions: SCCRO-induced invasion involves activation of MMP2 transcription in an AP2-and p53-dependent manner. SCCRO is a potential marker for metastatic progression in affected cancers.Cancer cell invasion and metastasis is a complex, multistep process involving interactions between invading cells, the extracellular matrix, and other stromal elements (1). Proteolytic enzymes secreted by tumor and/or host cells are required for cancer cells to invade the extracellular matrix and infiltrate lymphatic or blood vessel walls to metastasize to regional or distant sites. In addition, extracellular matrix proteolysis is also required for neoangiogenesis (2). Several studies suggest that matrix metalloproteinases (MMP), a family of zinc-dependent endopeptidases, play a significant role in extracellular matrix invasion (3). Two members of the MMP family, MMP2 (gelatinase A, 72-kDa type IV collagenase) and MMP9 (gelatinase B, 92-kDa type IV collagenase), are primarily responsible for invasion of the extracellular matrix and basement membrane. The expression of these gelatinases is relatively low in normal tissues and is induced when extracellular matrix remodeling is required. While gelatinase expression is primarily controlled at the transcriptional level, its activity is also regulated by posttranslational factors, including proenzyme activation by membrane-type MMPs and inhibition of enzyme activity by natural...