The past thirty years have reported the introduction of multiple anticancer therapies targeting various aspects of the cancer hallmarks, which are essential for successful tumor propagation and dissemination. In this sense, the evolution of molecular-scale technology has been central to the identification of new cancer targets.
The receptor tyrosine kinase (RTK) Hardy-Zuckerman 4 feline sarcoma virus homolog (c-KIT) is a critical regulator of growth, differentiation, migration and proliferation in the hematopoietic system, in germ cells and melanocytes. Since it activates a number of intracellular signaling pathways implicated in the tumor progression, it is one of the most studied proto-oncogenes as well as the target of drugs belonging to the family of tyrosine kinase inhibitors (TKIs). Actually, TKIs are employed for the treatment of human and canine c-KIT-dependent tumors as an alternative to standard chemotherapy. Nevertheless, multiple resistance phenomena frequently occur.
Recently, the discovery of G-quadruplex (G4) structures highlighted a new role for DNA in cancer biology. DNA G4 are four-stranded globular nucleic acid secondary structures, formed in specific G-rich sequences with biological significance; among these ones, the human telomeres and the promotorial region of oncogenes such as c-KIT.
In the first part of this dissertation, three compounds were proved to bind in silico c-KIT G4 and were tested in human and canine cell lines to check for their potential usefulness as therapeutic agents. Interesting results, e.g. c-KIT mRNA and protein inhibition, were obtained with an anthraquinone derivative (AQ1) that caused a block of cell proliferation.
In another study, the occurrence of c-KIT mutations was investigated in matched primary and metastatic canine cutaneous mast cell tumor (MCT), to make a recommendation for the best therapeutic choice. In dogs, 10-30% of MCTs possess c-KIT mutations, and the relevance of the mutational status for the therapy with TKIs is nowadays accepted also in this species; however, little is known on c-KIT mutational status in metastatic MCTs. In all analyzed dogs, there was a perfect concordance between c-KIT mutational status in primary MCT and the relative lymph node metastasis. This has a relevant implication for clinical practices.
Finally, during the Ph.D. program, a collaboration was established with the Centre de Recherche en Cancérologie de Marseille, and particularly with Dr. Patrice Dubreuil. In his most recent articles, he discovered a set of genes that are frequently mutated in human systemic mastocytosis (SM) and cooperate with c-KIT in the disease malignant evolution. In the last study illustrated in this Ph.D. thesis, the mutational profile of these hotspot genes in canine MCTs samples has been screened, in order to find molecular similarities between the two diseases, thereby justifying the use of domestic dog as an animal model in comparative oncology
