Vito Quaranta

Tumor Morphology and Phenotypic Evolution Driven by Selective Pressure from the Microenvironment

Emergence of invasive behavior in cancer is life-threatening, yet ill-defined due to its multifactorial nature. We present a multiscale mathematical model of cancer invasion, which considers cellular and microenvironmental factors simultaneously and interactively. Unexpectedly, the model simulations predict that harsh tumor microenvironment conditions (e.g., hypoxia, heterogenous extracellular matrix) exert a dramatic selective force on the tumor, which grows as an invasive mass with fingering margins, dominated by a few clones with aggressive traits. In contrast, mild microenvironment conditions (e.g., normoxia, homogeneous matrix) allow clones with similar aggressive traits to coexist with less aggressive phenotypes in a heterogeneous tumor mass with smooth, noninvasive margins. Thus, the genetic make-up of a cancer cell may realize its invasive potential through a clonal evolution process driven by definable microenvironmental selective forces. Our mathematical model provides a theoretical/experimental framework to quantitatively characterize this selective pressure for invasion and test ways to eliminate it.

A novel vitronectin receptor integrin (αvβx) is responsible for distinct adhesive properties of carcinoma cells

Abstract Carcinoma cells express a novel integrin involved in cell adhesion to vitronectin, but not to fibrinogen or von Willebrand factor, whereas melanoma and endothelial cells express a vitronectin receptor ( α v β 3 ) that promotes cell attachment to all of these matrix components. The integrin responsible for this adhesive phenotype of carcinoma cells is composed of an α subunit that is indistinguishable from the α v of the vitronectin receptor and a β subunit ( β x ) that is distinct from any known integrin β subunit. Accordingly, Northern blot analysis identifies an mRNA for α v , but not for β 3 in carcinoma cells. This receptor appears to mediate cell adhesion to vitronectin as well as fibronectin since an antibody directed to its α subunit blocked carcinoma cell adhesion to both of these matrix proteins. These results suggest that homologous integrins with identical α subunits and structurally distinct β subunits can account for the functional recognition of different matrixes by two cell types.

Integrative mathematical oncology

Cancer research attracts broad resources and scientists from many disciplines, and has produced some impressive advances in the treatment and understanding of this disease. However, a comprehensive mechanistic view of the cancer process remains elusive. To achieve this it seems clear that one must assemble a physically integrated team of interdisciplinary scientists that includes mathematicians, to develop mathematical models of tumorigenesis as a complex process. Examining these models and validating their findings by experimental and clinical observations seems to be one way to reconcile molecular reductionist with quantitative holistic approaches and produce an integrative mathematical oncology view of cancer progression.

A novel integrin (alpha E beta 4) from human epithelial cells suggests a fourth family of integrin adhesion receptors.

A new member of the integrin superfamily of adhesion receptors was isolated from human epithelial cells. Analogously to other integrins, this molecule is a heterodimer comprised of structurally unrelated subunits, both glycosylated. Unequivocal amino‐acid sequence homologies were observed between these subunits and integrin alpha and beta chain sequences, indicating that this epithelial heterodimer is a novel integrin. No obvious serologic cross‐reactivities were detected with other integrins. The beta chain of the epithelial integrin displayed a mol. wt significantly higher than other integrin beta chains, possibly due to a large sialic acid content. Integrin heterodimers are grouped into three families, based on which of three beta chains (beta 1, beta 2 and beta 3) they contain. Therefore, the epithelial integrin may represent the prototype of a fourth integrin family, because it contains a structurally distinct beta chain. The designation alpha E beta 4 is proposed for this novel human integrin.

Binding to EGF receptor of a laminin-5 EGF-like fragment liberated during MMP-dependent mammary gland involution

Extracellular matrix (ECM) fragments or cryptic sites unmasked by proteinases have been postulated to affect tissue remodeling and cancer progression. Therefore, the elucidation of their identities and functions is of great interest. Here, we show that matrix metalloproteinases (MMPs) generate a domain (DIII) from the ECM macromolecule laminin-5. Binding of a recombinant DIII fragment to epidermal growth factor receptor stimulates downstream signaling (mitogen-activated protein kinase), MMP-2 gene expression, and cell migration. Appearance of this cryptic ECM ligand in remodeling mammary gland coincides with MMP-mediated involution in wild-type mice, but not in tissue inhibitor of metalloproteinase 3 (TIMP-3)–deficient mice, supporting physiological regulation of DIII liberation. These findings indicate that ECM cues may operate via direct stimulation of receptor tyrosine kinases in tissue remodeling, and possibly cancer invasion.

Tumor cell α3β1 integrin and vascular laminin-5 mediate pulmonary arrest and metastasis

Arrest of circulating tumor cells in distant organs is required for hematogenous metastasis, but the tumor cell surface molecules responsible have not been identified. Here, we show that the tumor cell α3β1 integrin makes an important contribution to arrest in the lung and to early colony formation. These analyses indicated that pulmonary arrest does not occur merely due to size restriction, and raised the question of how the tumor cell α3β1 integrin contacts its best-defined ligand, laminin (LN)-5, a basement membrane (BM) component. Further analyses revealed that LN-5 is available to the tumor cell in preexisting patches of exposed BM in the pulmonary vasculature. The early arrest of tumor cells in the pulmonary vasculature through interaction of α3β1 integrin with LN-5 in exposed BM provides both a molecular and a structural basis for cell arrest during pulmonary metastasis.

Rapid Disruption of an Astrocyte Interaction With the Extracellular Matrix Mediated by Integrin α6β4 During Focal Cerebral Ischemia/Reperfusion

Background and Purpose Integrins participate in cerebral microvascular integrity and signaling during focal ischemia/reperfusion. The integrin subunits α1, α6, and β1 are distributed identically on normal cerebral microvessels. Studies in epithelium indicate that integrin α6β4, which interacts with laminin-5 in the basal lamina/extracellular matrix, is unique. This study describes the exact location of α6, β4, and α6β4 and that their responses in focal cerebral ischemia are relevant to astrocyte-matrix interactions. Methods The effect of middle cerebral artery occlusion and subsequent reperfusion on the microvascular expression of α6β4 and laminin-5 in regions of cellular injury (dUTP incorporation) was examined in 15 nonhuman primates. Well-characterized antibodies against human α6, β4, α6β4, laminin-5 and laminin-1, endothelial CD31, and vascular markers were measured with computerized video imaging and laser confocal microscopy. Results Integrin α6β4 was localized on astrocytes where it connects with the extracellular matrix at the astrocyte-vessel interface. It represented 59.3±16.4% of α6 antigen in cerebral microvessels <100 μm in diameter. By 2 hours of ischemia, the significant reduction in α6 expression (2 P <.001) was accompanied by decreases in β4/laminin-5 (0.76±0.03 to 0.20±0.09; 2 P =.001) and α6β4/laminin-5 (0.73±0.18 to 0.25±0.11; 2 P =.001) in the region of dUTP incorporation. Parallel changes in laminin-5 and laminin-1 were less pronounced and coincided by 24 hours. Conclusions This is the first description of a potential role of integrin α6β4 in the brain, where it mediates astrocyte-matrix interactions. The dramatic disappearance of α6β4 relative to its ligands reflects early loss of integrity between the astrocyte and the vessel wall in selected microvessels in response to ischemia.

Human Hepatocellular Carcinoma (HCC) Cells Require Both α3β1 Integrin and Matrix Metalloproteinases Activity for Migration and Invasion

Hepatocellular carcinoma (HCC) is the most frequent malignant tumor of the liver; prognosis depends on the tendency to metastasize. Cancer cell invasion is regulated by proteolytic remodeling of extracellular matrix components and by integrin expression. We have shown that matrix metalloproteinase-2 (MMP-2) and membrane-type–1 matrix metalloproteinase (MT1-MMP) cleave Laminin-5 (Ln-5), stimulating cell migration. Here we report that all HCC cells express MT1-MMP, migrate on Ln-1 and Collagen IV, whereas only HCC cells that express α3β1 integrin secrete detectable levels of gelatinases, migrate on Ln-5, and invade through a reconstituted basement membrane (BM). Migration on Ln-5 is blocked by BB-94, an MMP inhibitor, and by MIG1, a monoclonal antibody that hinders migration on MMP-2–cleaved Ln-5. Invasion through a reconstituted BM is also inhibited by BB-94. HCC α3β1-negative cells migrate on Ln-1 and Collagen IV, but not on Ln-5, and do not invade through a reconstituted BM, although they express MT1-MMP. Anti-α3β1 blocking antibodies inhibit gelatinase activation, cell motility, and cell invasion through Matrigel. In vivo, α3β1 integrin and Ln-5 are expressed in HCC tissue but not in normal liver. In conclusion, our data suggest that both α3β1 integrin and gelatinase activity are required for HCC migration and invasion.

Remodeling of the Microenvironment by Aggressive Melanoma Tumor Cells

Abstract: A necessity for development and tumor progression is a blood supply formed by vasculogenic and/or angiogenic events, involving the cooperative interactions of cells with their microenvironment. Based on the recent characterization of vasculogenic mimicry by aggressive melanoma cells, particularly their ability to express VE (vascular endothelial)‐cadherin, TIE‐1, and EphA2, current studies have focused on the molecular signals deposited by these cells as they remodel their microenvironment. The experimental approach utilizes unique three‐dimensional collagen matrices preconditioned by metastatic melanoma cells, which contain laminin 5 γ2 chain‐enriched tracks with promigratory cleavage fragments produced by cooperative interactions with specific matrix metalloproteinases (MMPs). The results demonstrate that the collagen matrices preconditioned by the metastatic cells induce poorly aggressive melanoma cells to express, for the first time, key angiogenic/vasculogenic/matrix‐remodeling genes. Treatment of aggressive melanoma cells with an MMP inhibitor resulted in the inhibition of vasculogenic mimicry‐associated genes in these tumor cells and abrogation of the inductive effects of the preconditioned matrix on poorly aggressive melanoma cells. These observations illustrate the remarkable influence of the microenvironment on the phenotype of melanoma cells and may provide new perspectives on tumor cell plasticity and unique treatment strategies.

Cadherin-Bound β-Catenin Feeds into the Wnt Pathway upon Adherens Junctions Dissociation: Evidence for an Intersection between β-Catenin Pools

β-catenin is an essential component of two cellular systems: cadherin-based adherens junctions (AJ) and the Wnt signaling pathway. A functional or physical connection between these β-catenin pools has been suggested in previous studies, but not conclusively demonstrated to date. To further examine this intersection, we treated A431 cell colonies with lysophosphatidic acid (LPA), which forces rapid and synchronized dissociation of AJ. A combination of immunostaining, time-lapse microscopy using photoactivatable-GFP-tagged β-catenin, and image analyses indicate that the cadherin-bound pool of β-catenin, internalized together with E-cadherin, accumulates at the perinuclear endocytic recycling compartment (ERC) upon AJ dissociation, and can be translocated into the cell nucleus upon Wnt pathway activation. These results suggest that the ERC may be a site of residence for β-catenin destined to enter the nucleus, and that dissociation of AJ may influence β-catenin levels in the ERC, effectively affecting β-catenin substrate levels available downstream for the Wnt pathway. This intersection provides a mechanism for integrating cell-cell adhesion with Wnt signaling and could be critical in developmental and cancer processes that rely on β-catenin-dependent gene expression.