The melanocortin-3 receptor is a pharmacological target for the regulation of anorexia.

Ablation of hypothalamic AgRP (Agouti-related protein) neurons is known to lead to fatal anorexia, whereas their activation stimulates voracious feeding and suppresses other motivational states including fear and anxiety. Despite the critical role of AgRP neurons in bidirectionally controlling feeding, there are currently no therapeutics available specifically targeting this circuitry. The melanocortin-3 receptor (MC3R) is expressed in multiple brain regions and exhibits sexual dimorphism of expression in some of those regions in both mice and humans. MC3R deletion produced multiple forms of sexually dimorphic anorexia that resembled aspects of human anorexia nervosa. However, there was no sexual dimorphism in the expression of MC3R in AgRP neurons, 97% of which expressed MC3R. Chemogenetic manipulation of arcuate MC3R neurons and pharmacologic manipulation of MC3R each exerted potent bidirectional regulation over feeding behavior in male and female mice, whereas global ablation of MC3R-expressing cells produced fatal anorexia. Pharmacological effects of MC3R compounds on feeding were dependent on intact AgRP circuitry in the mice. Thus, the dominant effect of MC3R appears to be the regulation of the AgRP circuitry in both male and female mice, with sexually dimorphic sites playing specialized and subordinate roles in feeding behavior. Therefore, MC3R is a potential therapeutic target for disorders characterized by anorexia, as well as a potential target for weight loss therapeutics.

Preclinical development of a bifunctional cancer cell homing, PKCepsilon inhibitory peptide for the treatment of head and neck cancer.

Head and neck squamous cell carcinoma (HNSCC) is the sixth most frequent cancer worldwide, comprising approximately 50% of all malignancies in some developing nations. Our recent work identified protein kinase Cepsilon (PKCepsilon) as a critical and causative player in establishing an aggressive phenotype in HNSCC. In this study, we investigated the specificity and efficacy of HN1-PKCepsilon, a novel bifunctional cancer cell homing, PKCepsilon inhibitory peptide, as a treatment for HNSCC. HN1-PKCepsilon peptide was designed by merging two separate technologies and synthesized as a capped peptide with two functional modules, HN1 (cancer cell homing) and PKCepsilon (specific PKCepsilon inhibitory), connected by a novel linker module. HN1-PKCepsilon preferentially internalized into UMSCC1 and UMSCC36 cells, two HNSCC cell lines, in comparison with oral epithelial cells: 82.1% positive for UMSCC1 and 86.5% positive for UMSCC36 compared with 1.2% positive for oral epithelial cells. In addition, HN1-PKCepsilon penetrated HNSCC cells in a dose- and time-dependent manner. Consistent with these in vitro observations, systemic injection of HN1-PKCepsilon resulted in selective delivery of HN1-PKCepsilon into UMSCC1 xenografts in nude mice. HN1-PKCepsilon blocked the translocation of active PKCepsilon in UMSCC1 cells, confirming HN1-PKCepsilon as a PKCepsilon inhibitor. HN1-PKCepsilon inhibited cell invasion by 72 +/- 2% (P < 0.001, n = 12) and cell motility by 56 +/- 2% (P < 0.001, n = 5) in UMSCC1 cells. Moreover, in vivo bioluminescence imaging showed that HN1-PKCepsilon significantly (83 +/- 1% inhibition; P < 0.02) retards the growth of UMSCC1 xenografts in nude mice. Our work indicates that the bifunctional HN1-PKCepsilon inhibitory peptide represents a promising novel therapeutic strategy for HNSCC.

Finding their groove; bifunctional molecules arrest growth of cancer cells.

In this issue, Dickinson et al. describe an exciting advance in the search for inhibitors of transcription that function well in cells . The authors screen for small molecules that selectively damage DNA and identify a histone gene as a potential new target for cancer therapeutic development.