Carcinoma matrix controls resistance to cisplatin through talin regulation of NF-kB.

Extracellular matrix factors within the tumor microenvironment that control resistance to chemotherapeutics are poorly understood. This study focused on understanding matrix adhesion pathways that control the oral carcinoma response to cisplatin. Our studies revealed that adhesion of HN12 and JHU012 oral carcinomas to carcinoma matrix supported tumor cell proliferation in response to treatment with cisplatin.

Integrin αβ1, αvβ, α6β effectors p130Cas, Src and talin regulate carcinoma invasion and chemoresistance.

Ligand engagement by integrins induces receptor clustering and formation of complexes at the integrin cytoplasmic face that controls cell signaling and cytoskeletal dynamics critical for adhesion-dependent processes. This study searches for a subset of integrin effectors that coordinates both tumor cell invasion and resistance to the chemotherapeutic drug cisplatin in oral carcinomas. Candidate integrin effectors were identified in a proteomics screen of proteins recruited to clustered integrin αβ1, α(v)β or α(6)β receptors in oral carcinomas.

beta1 integrin cytoplasmic domain residues selectively modulate fibronectin matrix assembly and cell spreading through talin and Akt-1.

The integrin beta(1) cytoplasmic domain (tail) serves as a scaffold for numerous intracellular proteins. The mechanisms by which the tail coordinates these proteins to facilitate extracellular matrix assembly and cell spreading are not clear. This study demonstrates that the beta(1) cytoplasmic domain can regulate cell spreading on fibronectin and fibronectin matrix assembly through Akt- and talin-dependent mechanisms, respectively.

Tac-beta1 inhibits FAK activation and Src signaling.

The binding of integrins to extracellular matrix triggers signals that promote cell spreading. We previously demonstrated that expression of the integrin beta1 cytoplasmic domain in the context of a chimeric transmembrane receptor with the Tac subunit of the interleukin-2 receptor (Tac-beta1) inhibits cell spreading. To study the mechanism whereby Tac-beta1 inhibits cell spreading, we examined the effect of Tac-beta1 on early signaling events following integrin engagement namely FAK and Src signaling.

Cell-matrix adhesion.

The complex interactions of cells with extracellular matrix (ECM) play crucial roles in mediating and regulating many processes, including cell adhesion, migration, and signaling during morphogenesis, tissue homeostasis, wound healing, and tumorigenesis. Many of these interactions involve transmembrane integrin receptors. Integrins cluster in specific cell-matrix adhesions to provide dynamic links between extracellular and intracellular environments by bi-directional signaling and by organizing the ECM and intracellular cytoskeletal and signaling molecules.

Cell-spreading assays.

A method is provided to quantitate the extent of cell spreading as a function of the expression level of transfected recombinant proteins. This chapter contains protocols for 1) replating and staining transfected cells for immunofluorescence microscopy, 2) optimizing image acquisition so that fluorescence intensity can be measured independent of cell morphology, and 3) quantitating cell area and expression levels of recombinant proteins for individual transfected cells using ImagePro-Plus software. This method can be used to further our understanding of intracellular signals and protein interactions that regulate cell spreading.

The integrin beta tail is required and sufficient to regulate adhesion signaling to Rac1.

Rac1 is a small Rho family GTPase that regulates changes in cell morphology associated with cell spreading and migration. Integrin-mediated adhesion is known to activate Rac1 and to regulate the interaction of Rac1 with downstream effectors. Currently, it is not clear how integrins signal Rac1 activation following cell adhesion.