Specific alpha v integrin receptors modulate K1735 murine melanoma cell behavior

Osteopontin is an endogenous modulator of the constitutively activated phenotype of pulmonary adventitial fibroblasts in hypoxic pulmonary hypertension

Increased cell proliferation and migration, of several cell types are key components of vascular remodeling observed in pulmonary hypertension (PH). Our previous data demonstrate that adventitial fibroblasts isolated from pulmonary arteries of chronically hypoxic hypertensive calves (termed PH-Fibs) exhibit a "constitutively activated" phenotype characterized by high proliferative and migratory potential. Osteopontin (OPN) has been shown to promote several cellular activities including growth and migration in cancer cells. We thus tested the hypothesis that elevated OPN expression confers the "activated" highly proproliferative and promigratory/invasive phenotype of PH-Fibs. Our results demonstrate that, both in vivo and ex vivo, PH-Fibs exhibited increased expression of OPN, as well as its cognate receptors, α(V)β(3) and CD44, compared with control fibroblasts (CO-Fibs). Augmented OPN expression in PH-Fibs corresponded to their high proliferative, migratory, and invasive properties and constitutive activation of ERK1/2 and AKT signaling. OPN silencing via small interfering RNA or sequestering OPN production by specific antibodies led to decreased proliferation, migration, invasion, and attenuated ERK1/2, AKT phosphorylation in PH-Fibs. Furthermore, increasing OPN levels in CO-Fibs via recombinant OPN resulted in significant increases in their proliferative, migratory, and invasive capabilities to the levels resembling those of PH-Fibs. Thus our data suggest OPN as an essential contributor to the activated (highly proliferative, migratory, and proinvasive) phenotype of pulmonary adventitial fibroblasts in hypoxic PH.

Tumor cell and carcinoma-associated fibroblast interaction regulates matrix metalloproteinases and their inhibitors in oral squamous cell carcinoma

Co-culture of periodontal ligament (PDL) fibroblasts and SCC-25 oral squamous carcinoma cells (OSCC), results in conversion of PDLs into carcinoma-associated fibroblasts (CAFs). Paracrin circuits between CAFs and OSCC cells were hypothesized to regulate the gene expression of matrix remodeling enzymes in their co-culture, which was performed for 7days, followed by analysis of the mRNA/protein expression and activity of metalloproteinases (MMPs), their tissue inhibitors (TIMPs) and other relevant genes. Interleukin1-β, transforming growth factor-β1, fibronectin and αvβ6 integrin have shown to be involved in the regulation of the MMP and TIMP gene expression in co-culture of CAFs and tumor cells. In addition, these cells also cooperated in activation of MMP pro-enzymes. It is particularly interesting that the fibroblast-produced inactive MMP-2 has been activated by the tumor-cell-produced membrane-type 1 matrix metalloproteinase (MT1-MMP). The crosstalk between cancer- and the surrounding fibroblast stromal-cells is essential for the fine tuning of cancer cells invasivity.

Role of integrins in regulating proteases to mediate extracellular matrix remodeling

The extracellular matrix (ECM) is an extracellular scaffold composed of complex mixtures of proteins that plays a pivotal role in tumor progression. ECM remodeling is crucial for tumor migration and invasion during the process of metastasis. ECM can be remodeled by several processes including synthesis, contraction and proteolytic degradation. In order to cross through the ECM barriers, malignant cells produce a spectrum of extracellular proteinases including matrix metalloproteinases (MMPs), serine proteases (mainly the urokinase plasminogen activator (uPA) system) and cysteine proteases to degrade ECM components. As major adhesion molecules to support cell attachment to ECM, integrins play critical roles in tumor progression by enhancing tumor cell survival, migration and invasion. Previous studies have shown that integrins can regulate the expression and activity of these proteases through different pathways. This review summarizes the roles of MMPs and uPA system in ECM remodeling and discusses the regulatory functions of integrins on these proteases in invasive tumors.

Positive crosstalk between ERK and p38 in melanoma stimulates migration and in vivo proliferation

Melanoma is one of the most therapy-resistant cancers. Activating mutations in BRAF and NRAS are the source of extracellular signal regulated protein kinase (ERK) pathway activation. We show that melanoma cell lines, originating in different metastatic sites, with BRAF or NRAS mutations, in addition to active mitogen activated protein kinase (MAPK)-ERK, also have highly activated stress activated protein kinase (SAPK)-p38. This is in direct contrast to carcinoma cells in which the activity of the two kinases appears to be mutually exclusive; high level of p38 activity inhibits, through a negative feedback, ERK activity and prevents tumorigenesis. Melanomas are insensitive to ERK inhibition by p38 and utilize p38-signaling pathway for migration and growth in vivo. We found a positive functional loop linking the high ERK activity to surface expression of alphaVbeta3-integrin. This integrin, by interacting with vitronectin, induces p38 activity and increases IL-8 production, enhancing cell migration. Because the negative loop from p38 to ERK is lost, the two kinases can remain simultaneously activated. Inhibition of ERK and p38 activities is more effective in blocking in vivo growth than inhibition of each kinase individually. Future therapies might have to consider targeting of both pathways.

A randomized multi-center phase II trial of the angiogenesis inhibitor Cilengitide (EMD 121974) and gemcitabine compared with gemcitabine alone in advanced unresectable pancreatic cancer

Background

Anti-angiogenic treatment is believed to have at least cystostatic effects in highly vascularized tumours like pancreatic cancer. In this study, the treatment effects of the angiogenesis inhibitor Cilengitide and gemcitabine were compared with gemcitabine alone in patients with advanced unresectable pancreatic cancer.

Methods

A multi-national, open-label, controlled, randomized, parallel-group, phase II pilot study was conducted in 20 centers in 7 countries. Cilengitide was administered at 600 mg/m² twice weekly for 4 weeks per cycle and gemcitabine at 1000 mg/m² for 3 weeks followed by a week of rest per cycle. The planned treatment period was 6 four-week cycles. The primary endpoint of the study was overall survival and the secondary endpoints were progression-free survival (PFS), response rate, quality of life (QoL), effects on biological markers of disease (CA 19.9) and angiogenesis (vascular endothelial growth factor and basic fibroblast growth factor), and safety. An ancillary study investigated the pharmacokinetics of both drugs in a subset of patients.

Results

Eighty-nine patients were randomized. The median overall survival was 6.7 months for Cilengitide and gemcitabine and 7.7 months for gemcitabine alone. The median PFS times were 3.6 months and 3.8 months, respectively. The overall response rates were 17% and 14%, and the tumor growth control rates were 54% and 56%, respectively. Changes in the levels of CA 19.9 went in line with the clinical course of the disease, but no apparent relationships were seen with the biological markers of angiogenesis. QoL and safety evaluations were comparable between treatment groups. Pharmacokinetic studies showed no influence of gemcitabine on the pharmacokinetic parameters of Cilengitide and vice versa.

Conclusion

There were no clinically important differences observed regarding efficacy, safety and QoL between the groups. The observations lay in the range of other clinical studies in this setting. The combination regimen was well tolerated with no adverse effects on the safety, tolerability and pharmacokinetics of either agent.

Loss of dipeptidyl peptidase IV immunostaining discriminates malignant melanomas from deep penetrating nevi

The deep penetrating nevus is a rare variant of benign melanocytic nevus with histologic features mimicking vertical growth phase, nodular malignant melanoma. In this study, we expand on the search for new complementary discriminating markers by analyzing a selection of both cell cycle-related factors, such as retinoblastoma protein and phospho-retinoblastoma protein Ser795 as indicators for retinoblastoma protein activation/inactivation status, and invasion-related factors, such as matrix metalloproteinase-1, matrix metalloproteinase-2, membrane-type matrix metalloproteinase-1 and integrin beta3. MIB-1/Ki-67 was analyzed as an example for a common proliferation marker. Dipeptidyl peptidase IV/CD26 was analyzed as a marker affecting both proliferation and invasion of malignant melanocytic tumors. Semiquantitative assessment of both immunolocalization and immunoreactivity of retinoblastoma protein and phospho-retinoblastoma protein Ser795, MIB-1/Ki-67, matrix metalloproteinase-1, matrix metalloproteinase-2, membrane-type matrix metalloproteinase-1 and integrin beta3 revealed no consistent differences between deep penetrating nevi (n=14) and matched cases of nodular malignant melanomas (n=10). Matrix metalloproteinase-1 and matrix metalloproteinase-2 immunostaining of some deep penetrating nevi even exceeded that of nodular malignant melanomas. Membrane-type matrix metalloproteinase-1 expression scores of nodular malignant melanomas were higher than those of deep penetrating nevi, which was, however, not significantly discriminative. In contrast, immunostaining of dipeptidyl peptidase IV was significantly discriminative due to a consistent lack of dipeptidyl peptidase IV-expression in nodular malignant melanomas. These results add evidence that among the selected markers supposed to be relevant for melanoma progression the presence of dipeptidyl peptidase IV can be used to support diagnosis of deep penetrating nevi in doubtful cases. As loss of dipeptidyl peptidase IV may also be causally linked to the transition of invasive to metastatic phenotypes, the molecular mechanisms downstream of dipeptidyl peptidase IV deserve to be studied in more detail in future investigations.

Alpha-V-dependent outside-in signaling is required for the regulation of CD44 surface expression, MMP-2 secretion, and cell migration by osteopontin in human melanoma cells

The level of integrin alpha(v)beta3 and its ligand osteopontin (OPN) has been directly correlated to tumorigenicity of melanoma and other cancer cells. We have previously shown an increase in pp(60c-Src) kinase activity associated with integrin alpha(v)beta3 in melanoma cells (M21) treated with soluble OPN. pp(60c-Src) kinase activity was not observed in melanoma cells expressing alpha(v) that lacks the cytoplasmic domain (alpha(v)995). Results of the current study demonstrate that the amino acid sequence '995RPPQEEQERE1004' in the beta-turn of alpha(v) chain is required for the interaction of pp(60c-Src). Our results suggest that the beta-turn of alpha(v) chain may be indispensable for alpha(v)-associated signaling complex formation and outside-in signaling. To further analyze the alpha(v)beta3 signaling in melanoma cells, we over expressed OPN in M21 cells (M21/OPN). CD44 surface expression and MMP-2 activity in the conditioned medium were increased to a greater extent in M21/OPN cells as compared with M21 or alpha(v)995 cells. Also, M21/OPN cells exhibit increased motility, which is markedly reduced upon treatment with inhibitors to alpha(v) and MMP-2. Our findings suggest that the increase in MMP-2 activity is integrin-dependent as MMP-2 activity is reduced in cells treated with an inhibitor to alpha(v) or in alpha(v)995 cells expressing mutant alpha(v).

Alphavbeta3 integrin and cofilin modulate K1735 melanoma cell invasion

Cytoskeletal reorganization is partially mediated through cofilin, an actin assembly regulatory protein. Cofilin activity is modulated by reversible phosphorylation at Ser3. In this study, using K1735 murine melanoma cells, we examined the relationship between beta3-integrin expression, phosphorylation of cofilin, and metalloproteinase production. The levels of phosphorylated cofilin were 10-fold higher in cells expressing alphavbeta3 than in alphavbeta3-negative cells when plated on vitronectin for 30 min. However, by 60 min, phosphorylation of cofilin was greater in the beta3-negative cells. Expression of the wild type (WT) or non-phosphorylatable cofilin (A3 mutant) increased melanoma cell migration on vitronectin and invasion through a reconstituted basement membrane. Expression of a pseudophosphorylated, poorly active cofilin (E3 mutant) reduced cell motility. Expression of active cofilin accelerated the phosphorylation of FAK at Y397 and at Y576, strongly implicating cofilin as a mediator of cell signaling. The expression of MT1-MMP and MMP2 was also increased by expression of wild type or A3 cofilin. A 50% reduction of both enzymes was observed by the expression of the E3 cofilin. Overexpression of non-phosphorylatable cofilin was sufficient to induce the expression of MT1-MMP and MMP2 in the beta3-negative M2Tbeta3 cells. Interestingly, the invasion of M2Tbeta3 cells could be sustained by overexpression of cofilin A3. These results suggest that the integrin alphavbeta3 and cofilin together regulate K1735 melanoma cell invasion.

Specific amino acid restriction inhibits attachment and spreading of human melanoma via modulation of the integrin/focal adhesion kinase pathway and actin cytoskeleton remodeling

We had previously found that selective restriction of amino acids inhibits invasion of human A375 melanoma. Integrins, cell surface receptors for the components of extracellular matrix (ECM), are activated during cell adhesion and spreading, and initiate signaling pathways that control growth and invasion of tumor cells. We examined the effect of tyrosine (Tyr) and phenylalanine (Phe), methionine (Met) or glutamine (Gln) restriction on attachment and spreading of A375 and MeWo melanoma cell lines on fibronectin and laminin. In A375 cells, restriction of Tyr/Phe or Met inhibited attachment to and spreading on laminin and fibronectin, inhibited alpha3 and alpha4 integrin expression, and inhibited accumulation of FAK-Tyr397 and F-actin at leading edges of cell protrusions. Tyr/Phe restriction also inhibited attachment-induced autophosporylation of FAK-Tyr397. In MeWo cells, the order of inhibition by amino acid restriction on cell attachment and spreading was as follows: Gln > Tyr/Phe > Met. Restriction of Gln reduced alpha5 integrin expression. All amino acid restrictions similarly inhibited phosphorylation of FAK-Tyr397, FAK-Tyr577, FAK-Tyr861 and paxillin-Tyr31. Gln restriction exhibited the strongest inhibition of actin cytoskeleton remodeling during the cell spreading. The present study reveals that specific amino acid restriction inhibits attachment and spreading of melanoma via inhibition of specific integrin expression, inhibition of integrin-mediated FAK phosphorylation, and modulation of actin cytoskeleton remodeling. These data provide additional understanding of the mechanism by which specific amino acid restriction controls invasion and migration of melanoma.

Tenascin-C deposition requires β3 integrin and Src

In this study we now show that deposition of the mesenchymal matrix marker, tenascin-C (TN-C), is mediated through beta3 expression and activation of Src. There was a striking upregulation of TN-C matrix organization in cell lines expressing beta3 and activated Src when compared to cell lines with neither of these attributes. When beta3 function was suppressed so was the deposition of TN-C. The same was true for function and activation of Src. When Src was inactive, the deposition of TN-C was low. We also determined that one of the downstream effectors of Src, MAPK, was also required to promote TN-C deposition. When MAPK activation was inhibited, TN-C deposition was also decreased. MMP activation is also implicated in TN-C deposition. The broad spectrum MMP inhibitor, GM6001, suppressed TN-C organization. These results indicate that beta3 integrin ligand binding and the activation of the Src/MAPK/MMP pathway modulate deposition of TN-C.