MMP-2 functions as an early response protein in ovarian cancer metastasis

The significance of MMP-9 over MMP-2 in HCC invasiveness and recurrence of hepatocellular carcinoma after curative resection

BACKGROUND

The extracellular matrix metalloproteases MMP-9 and MMP-2 are critical for the invasive potential of tumors. However, it is not clear which of the two plays the predominant role in tumor invasion and progression. In the present study, we compared the clinical efficacy of MMP-9 and MMP-2 overexpression for predicting tumor recurrence and survival after surgical resection in HCC patients.

MATERIALS AND METHODS

MMP-9 and MMP-2 expression in HCC cell lines and in vitro HCC invasion model were detected by quantitative RT-PCR and immunofluorescence. The expression levels of MMP-9 and MMP-2 were assessed by immunohistochemistry in HCC tissue microarrays from HCC patients (study set) who underwent curative resection. The clinicopathological data were retrospectively analyzed. The results were further verified in an independent cohort of 92 HCC patients (validation set).

RESULTS

Univariate analysis demonstrated that high expression of MMP-9 was associated with both time to recurrence (TTR, P = .015) and overall survival (OS, P = .024), whereas high expression of MMP-2 was only correlated with TTR (P = .041). Multivariate analysis confirmed that MMP-9 expression was an independent predictor of TTR and OS. The coindex of MMP-9 and preoperative serum AFP levels was significantly correlated with TTR and OS (P = .036 and P = .040), but the coindex of MMP-2 and AFP did not show prognostic significance for either TTR or OS (P = .067 and P = .053). The prognostic value of MMP-9 overexpression was validated in the independent data set.

CONCLUSION

MMP-9 is superior to MMP-2 for the prediction of tumor recurrence and survival in HCC patients after surgical resection.

Ligand-independent activation of c-Met by fibronectin and α(5)β(1)-integrin regulates ovarian cancer invasion and metastasis

The role of the fibronectin receptor, α₅β₁-integrin, as an adhesion receptor and in angiogenesis, is well established. However, its role in cancer cell invasion and metastasis is less clear. We describe a novel mechanism by which fibronectin regulates ovarian cancer cell signaling and promotes metastasis. Fibronectin binding to α₅β₁-integrin led to a direct association of α₅-integrin with the receptor tyrosine kinase, c-Met, activating it in a hepatocyte growth factor/scatter factor (HGF/SF) independent manner. Subsequently, c-Met associated with Src and activated Src and focal adhesion kinase (FAK). Inhibition of α₅β₁-integrin decreased the phosphorylation of c-Met, FAK and Src, both in vitro and in vivo. Independent activation of c-Met by its native ligand, HGF/SF, or overexpression of a constitutively active FAK in HeyA8 cells could overcome the effect of α₅β₁-integrin inhibition on tumor cell invasion, indicating that α₅β₁-integrin is upstream of c-Met, Src and FAK. Inhibition of α₅β₁-integrin on cancer cells in two xenograft models of ovarian cancer metastasis resulted in a significant decrease of tumor burden, which was independent of the effect of α₅β₁-integrin on angiogenesis. These data suggest that fibronectin promotes ovarian cancer invasion and metastasis through an α₅β₁-integrin/c-Met/FAK/Src dependent signaling pathway, transducing signals through c-Met in a HGF/SF independent manner.

Ovarian cancer development and metastasis

The biology of ovarian carcinoma differs from that of hematogenously metastasizing tumors because ovarian cancer cells primarily disseminate within the peritoneal cavity and are only superficially invasive. However, since the rapidly proliferating tumors compress visceral organs and are only temporarily chemosensitive, ovarian carcinoma is a deadly disease, with a cure rate of only 30%. There are a number of genetic and epigenetic changes that lead to ovarian carcinoma cell transformation. Ovarian carcinoma could originate from any of three potential sites: the surfaces of the ovary, the fallopian tube, or the mesothelium-lined peritoneal cavity. Ovarian cacinoma tumorigenesis then either progresses along a stepwise mutation process from a slow growing borderline tumor to a well-differentiated carcinoma (type I) or involves a genetically unstable high-grade serous carcinoma that metastasizes rapidly (type II). During initial tumorigenesis, ovarian carcinoma cells undergo an epithelial-to-mesenchymal transition, which involves a change in cadherin and integrin expression and up-regulation of proteolytic pathways. Carried by the peritoneal fluid, cancer cell spheroids overcome anoikis and attach preferentially on the abdominal peritoneum or omentum, where the cancer cells revert to their epithelial phenotype. The initial steps of metastasis are regulated by a controlled interaction of adhesion receptors and proteases, and late metastasis is characterized by the oncogene-driven fast growth of tumor nodules on mesothelium covered surfaces, causing ascites, bowel obstruction, and tumor cachexia.

Strategies for high-resolution imaging of epithelial ovarian cancer by laparoscopic nonlinear microscopy

Ovarian cancer remains the most frequently lethal of the gynecologic cancers owing to the late detection of this disease. Here, by using human specimens and three mouse models of ovarian cancer, we tested the feasibility of nonlinear imaging approaches, the multiphoton microscopy (MPM) and second harmonic generation (SHG) to serve as complementary tools for ovarian cancer diagnosis. We demonstrate that MPM/SHG of intrinsic tissue emissions allows visualization of unfixed, unsectioned, and unstained tissues at a resolution comparable to that of routinely processed histologic sections. In addition to permitting discrimination between normal and neoplastic tissues according to pathological criteria, the method facilitates morphometric assessment of specimens and detection of very early cellular changes in the ovarian surface epithelium. A red shift in cellular intrinsic fluorescence and collagen structural alterations have been identified as additional cancer-associated changes that are indiscernible by conventional pathologic techniques. Importantly, the feasibility of in vivo laparoscopic MPM/SHG is demonstrated by using a "stick" objective lens. Intravital detection of neoplastic lesions has been further facilitated by low-magnification identification of an indicator for cathepsin activity followed by MPM laparoscopic imaging. Taken together, these results demonstrate that MPM may be translatable to clinical settings as an endoscopic approach suitable for high-resolution optical biopsies as well as a pathology tool for rapid initial assessment of ovarian cancer samples.

The IGF-I receptor can alter the matrix metalloproteinase repertoire of tumor cells through transcriptional regulation of PKC-{alpha}

The IGF-I receptor (IGF-IR) was identified as a tumor progression factor, but its role in invasion and metastasis has been the subject of some controversy. Previously we reported that in murine lung carcinoma M-27 cells, overexpression of IGF-IR increased the synthesis and activation of matrix metalloproteinase (MMP)-2 via Akt/phosphatidylinositol 3-kinase signaling. In contrast, we show here that in these and other cells, IGF-IR overexpression reduced the constitutive and phorbol 12-myristate 13-acetate (PMA)-inducible expression of three protein kinase C (PKC)-regulated metalloproteinases, MMP-3, MMP-9, and MMP-13, in cultured cells as well as in vivo in sc tumors. To elucidate the underlying mechanism, we analyzed the effect of IGF-IR on PKC expression and activity using wild-type and IGF-IR-overexpressing (M-27(IGFIR)) tumor cells. Our results show that overexpression and activation of IGF-IR reduced PKC-alpha expression, PKC activity, and downstream ERK1/2 signaling, and these effects were reversed in cells expressing kinase (Y(1131,1135,1136)F) or C-terminal (Y(1250/51)F) domain mutants of IGF-IR. This reduction was due to transcriptional down-regulation of PKC-alpha as evidenced by reduced PKC-alpha mRNA expression in a phosphatidylinositol 3-kinase-dependent manner and a blockade of PKC-alpha promoter activation as revealed by a reporter gene assay. Finally, reconstitution of PKC-alpha levels could restore MMP-9 expression levels in these cells. Collectively, these results show that IGF-IR can inhibit PKC-alpha gene transcription and thereby block the synthesis of PMA-regulated MMPs, suggesting that within the same cells, IGF-IR can act as both a positive and negative regulator of MMP expression and function.