Fibronectin conformation regulates the proangiogenic capability of tumor-associated adipogenic stromal cells.

BACKGROUND: Changes in fibronectin (Fn) matrix remodeling contribute to mammary tumor angiogenesis and are related to altered behavior of adipogenic stromal cells; yet, the underlying mechanisms remain unclear due in part to a lack of reductionist model systems that allow the inherent complexity of cell-derived extracellular matrices (ECMs) to be deciphered. In particular, breast cancer-associated adipogenic stromal cells not only enhance the composition, quantity, and rigidity of deposited Fn, but also partially unfold these matrices. However, the specific effect of Fn conformation on tumor angiogenesis is undefined. METHODS: Decellularized matrices and a conducting polymer device consisting of poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) were used to examine the effect of Fn conformation on the behavior of 3T3-L1 preadipocytes. Changes in cell adhesion and proangiogenic capability were tested via cell counting and by quantification of vascular endothelial growth factor (VEGF) secretion, respectively. Integrin-blocking antibodies were utilized to examine varied integrin specificity as a potential mechanism. RESULTS: Our findings suggest that tumor-associated partial unfolding of Fn decreases adhesion while enhancing VEGF secretion by breast cancer-associated adipogenic precursor cells, and that altered integrin specificity may underlie these changes. CONCLUSIONS AND GENERAL SIGNIFICANCE: These results not only have important implications for our understanding of tumorigenesis, but also enhance knowledge of cell-ECM interactions that may be harnessed for other applications including advanced tissue engineering approaches. This article is part of a Special Issue entitled Organic Bioelectronics - Novel Applications in Biomedicine.

Implanted adipose progenitor cells as physicochemical regulators of breast cancer.

Multipotent adipose-derived stem cells (ASCs) are increasingly used for regenerative purposes such as soft tissue reconstruction following mastectomy; however, the ability of tumors to commandeer ASC functions to advance tumor progression is not well understood. Through the integration of physical sciences and oncology approaches we investigated the capability of tumor-derived chemical and mechanical cues to enhance ASC-mediated contributions to tumor stroma formation. Our results indicate that soluble factors from breast cancer cells inhibit adipogenic differentiation while increasing proliferation, proangiogenic factor secretion, and myofibroblastic differentiation of ASCs. This altered ASC phenotype led to varied extracellular matrix (ECM) deposition and contraction thereby enhancing tissue stiffness, a characteristic feature of breast tumors. Increased stiffness, in turn, facilitated changes in ASC behavior similar to those observed with tumor-derived chemical cues. Orthotopic mouse studies further confirmed the pathological relevance of ASCs in tumor progression and stiffness in vivo. In summary, altered ASC behavior can promote tumorigenesis and, thus, their implementation for regenerative therapy should be carefully considered in patients previously treated for cancer.

Stiffness of photocrosslinked RGD-alginate gels regulates adipose progenitor cell behavior.

Adipose progenitor cells (APCs) are widely investigated for soft tissue reconstruction following tumor resection; however, the long-term success of current approaches is still limited. In order to develop clinically relevant therapies, a better understanding of the role of cell-microenvironment interactions in adipose tissue regeneration is essential. In particular, the effect of extracellular matrix (ECM) mechanics on the regenerative capability of APCs remains to be clarified. We have used artificial ECMs based on photocrosslinkable RGD-alginate to investigate the adipogenic and pro-angiogenic potential of 3T3-L1 preadipocytes as a function of matrix stiffness. These hydrogels allowed us to decouple matrix stiffness from changes in adhesion peptide density or extracellular Ca(2+) concentration and provided a physiologically relevant 3D culture context. Our findings suggest that increased matrix rigidity promotes APC self-renewal and angiogenic capacity, whereas, it inhibits adipose differentiation. Collectively, this study advances our understanding of the role of ECM mechanics in adipose tissue formation and vascularization and will aid in the design of efficacious biomaterial scaffolds for adipose tissue engineering applications.

Tissue-engineered three-dimensional tumor models to study tumor angiogenesis.

Cell-microenvironment interactions play a critical role in the transformation of normal cells into cancer; however, the underlying mechanisms and effects are far from being well understood. Tissue Engineering provides innovative culture tools and strategies to study tumorigenesis under pathologically relevant culture conditions. Specifically, integration of biomaterials, scaffold fabrication, and micro/nano-fabrication techniques offers great promise to reveal the dynamic role of chemical, cell-cell, cell-extracellular matrix, and mechanical interactions in the pathogenesis of cancer. Due to the central importance of blood vessel formation in tumor growth, progression, and drug response, this review will discuss specific design parameters for the development of culture microenvironments to study tumor angiogenesis. Tumor engineering approaches have the potential to revolutionize our understanding of cancer, provide new platforms for testing of anti-cancer drugs, and may ultimately result in improved treatment strategies.

Parylene peel-off arrays to probe the role of cell-cell interactions in tumour angiogenesis.

Microenvironmental conditions impact tumour angiogenesis, but the role of cell-cell interactions in modulating the angiogenic capability of tumour cells is not well understood. We have microfabricated a peel-off cell-culture array (PeelArray) chip to spatiotemporally control interactions between tumour cells in a large array format and to analyse angiogenic factor secretion in response to these conditions. The PeelArray chip consists of a polyethylene glycol (PEG) treated glass coverslip coated with a parylene-C template that can be easily peeled off to selectively micropattern biomolecules and cells. We have designed the PeelArray chip to reproducibly deposit large uniform arrays of isolated single cells or isolated cell clusters on fibronectin features of defined surface areas. We have utilised this microfabricated culture system to study the secretion of angiogenic factors by tumour cells, in the presence or absence of cell-cell contact as controlled by micropatterning. Our results indicate that cell-cell interactions play a synergistic role in regulating the expression of angiogenic factors (i.e., vascular endothelial growth factor [VEGF] and interleukin-8 [IL-8]) in various cancer cell lines, independent of other more complex microenvironmental cues (e.g. hypoxia). Our PeelArray chip is a simple and adaptable micropatterning method that enables quantitative profiling of protein secretions and hence, a better understanding of the mechanisms by which cell-cell interactions regulate tumour cell behaviour and angiogenesis.