Antitumor monoclonal antibodies have shown clinical promise as cancer cell surface targeting agents. More tumor targeting antibodies are likely to be approved by the FDA in the next few years. However, there are two major limitations in antibody-targeted therapy: large size and nonspecific uptake of the antibody molecules by the liver and the reticuloendothelial system. These result in poor tumor penetration of antibody pharmaceuticals and dose-limiting toxicity to the liver and bone marrow. Peptides are excellent alternative targeting agents for human cancers, and they may alleviate some of the problems with antibody targeting. In the last decade, several investigators have successfully used combinatorial library methods to discover cell surface binding peptides that may be useful for cancer targeting. The phage-display library technique and the "one-bead one-compound" combinatorial library method are the two approaches that have been used. Cancer cell surface receptors or endothelial cell surface receptors of the neovasculature are the two popular therapeutic targets for cancer. Results from preclinical studies with some peptides are encouraging in their targeting potential.

Cell motility is partially dependent on interactions between the integrins and the extracellular matrix. Our previous studies have identified synthetic D-amino acid cell adhesion peptides using a combinatorial screening approach. In this study, we demonstrate that HYD1 (kikmviswkg) completely blocks random haptotactic migration and inhibits invasion of prostate carcinoma cells on laminin-5. This effect is adhesion independent and reversible. The inhibition of migration by HYD1 involves a dramatic remodeling of the actin cytoskeleton resulting in increased stress fiber formation and actin colocalization with cortactin at the cell membrane. HYD1 interacts with alpha6beta1 (not alpha6beta4) and alpha3beta1 integrins and surprisingly elevates laminin-5-dependent intracellular signals including focal adhesion kinase, mitogen-activated protein kinase kinase and extracellular signal-regulated kinase. HYD1 does not contain a previously characterized binding sequence for integrins. A scrambled derivative of HYD1, called HYDS (wiksmkivkg), does not interact with the alpha6 or alpha3 integrin subunits and is not biologically active. Taken together, these results indicate that HYD1 is a biologically active integrin-targeting peptide that reversibly inhibits tumor cell migration on laminin-5 and uncouples phosphotyrosine signaling from cytoskeletal-dependent migration.

We have developed a cell model to investigate steroid control of differentiation using a subline of HT1080 cells (HT-AR1) that have been engineered to express the human androgen receptor. Dihydrotestosterone (DHT) treatment of HT-AR1 cells induced growth arrest and cytoskeletal reorganization that was associated with the expression of fibronectin and the neuroendocrine markers chromogranin A and neuron-specific enolase. Expression profiling analysis identified the human FERM domain-encoding gene EHM2 as uniquely induced in HT-AR1 cells as compared to 16 other FERM domain containing genes. Since FERM domain proteins control cytoskeletal functions in differentiating cells, and the human EHM2 gene has not been characterized, we investigated EHM2 steroid-regulation, genomic organization, and sequence conservation. We found that DHT, but not dexamethasone, induced the expression of a 3.8 kb transcript in HT-AR1 cells encoding a 504 amino acid protein, and moreover, that human brain tissue contains a 5.8 kb transcript encoding a 913 amino acid isoform. Construction of an unrooted phylogenetic tree using 98 FERM domain proteins revealed that the human EHM2 gene is a member of a distinct subfamily consisting of nine members, all of which contain a highly conserved 325 amino acid FERM domain.

Compared to younger patients, elderly patients with locally advanced head and neck cancer tolerated chemoradiation with IMRT and IGRT well, and should not be denied curative treatment based solely on age.

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