RON - The Con in Colorectal Carcinoma

The recepteur d’origine nantais (RON) is a member of MET family of receptor tyrosine kinase (RTKs), an overexpression of which has been observed in several cancers. The expression of RON gene is required during embryonic development and also plays critical roles in regulating macrophage inflammatory response. In CRC, the overexpression of moderate RON activity contributes to their oncogenic potential by regulating several key processes such as proliferation, motility and resistance to apoptosis. Interestingly, an aberrant RON expression is often associated with the generation of several splice variants with unique transforming activities. The targeting of RON signaling pathway by the use of mono-clonal antibodies and small-molecule inhibitors has shown promising therapeutic results in animal models. The present ar-ticle aims at summarizing the current understanding of RON kinase in CRC

Generation of a Retinoblastoma (Rb)1-inducible dominant-negative (DN) mouse model.

Retinoblastoma 1 (Rb1) is an essential gene regulating cellular proliferation, differentiation, and homeostasis. To exert these functions, Rb1 is recruited and physically interacts with a growing variety of signaling pathways. While Rb1 does not appear to be ubiquitously expressed, its expression has been confirmed in a variety of hematopoietic and neuronal-derived cells, including the inner ear hair cells (HCs). Studies in transgenic mice demonstrate that complete germline or conditional Rb1 deletion leads to abnormal cell proliferation, followed by massive apoptosis; making it difficult to fully address Rb1\u27s biochemical activities. To overcome these limitations, we developed a tetracycline-inducible TetO-CB-myc6-Rb1 (CBRb) mouse model to achieve transient and inducible dominant-negative (DN) inhibition of the endogenous RB1 protein. Our strategy involved fusing the Rb1 gene to the lysosomal protease pre-procathepsin B (CB), thus allowing for further routing of the DN-CBRb fusion protein and its interacting complexes for proteolytic degradation. Moreover, reversibility of the system is achieved upon suppression of doxycycline (Dox) administration. Preliminary characterization of DN-CBRb mice bred to a ubiquitous rtTA mouse line demonstrated a significant inhibition of the endogenous RB1 protein in the inner ear and in a number of other organs where RB1 is expressed. Examination of the postnatal (P) DN-CBRb mice inner ear at P10 and P28 showed the presence of supernumerary inner HCs (IHCs) in the lower turns of the cochleae, which corresponds to the described expression domain of the endogenous Rb1 gene. Selective and reversible suppression of gene expression is both an experimental tool for defining function and a potential means to medical therapy. Given the limitations associated with Rb1-null mice lethality, this model provides a valuable resource for understanding RB1 activity, relative contribution to HC regeneration and its potential therapeutic application