Antitumor effect of SOS-1/KRAS inhibitor BAY-293 against head and neck carcinoma

Head and neck cancer (HNC) is a heterogeneous disease that affects multiple anatomical sites and histological subtypes. Among these tumors, head and neck thyroid cancer is one of the endocrine-derived HNC. The most aggressive and lethal type of thyroid cancer (TC) is anaplastic thyroid carcinoma (ATC). Another aggressive type of HNC is oral squamous cell carcinoma (OSCC) which originates in the squamous cells lining the mucosa of the mouth. Although ATC and OSCC are two totally different types of tumors in terms of origin, prognosis, and treatment, a known oncogene common in the pathogenesis of both tumors is the Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) oncogene. Recent studies have indicated that increased expression levels of mutated KRAS genes may play a key role in the development and progression of ATC and OSCC. KRAS is one of the well-known proto-oncogenes that belongs to a group of small guanosine triphosphate (GTP)-binding proteins known as the RAS superfamily or RAS-like GTPases. Overexpression of KRAS can be caused by a mutation of the KRAS gene or by hyperactivation of growth factor receptor tyrosine kinases. Despite its recognized importance in cancer malignancy, KRAS is considered non-druggable and has been never studied in the field of HNC. Recently, it has been shown that an interesting approach to target K-RAS and its interaction with GTP cargo could be through the Son of Sevenless 1 (SOS1) protein, a key regulator of KRAS function. In this context, a new synthetic molecule, BAY-293, has recently been developed, able to selectively inhibits the KRAS–SOS1 interaction. Based on these findings, the aim of this thesis was to evaluate for the first time the antitumor effect of BAY-293 in the field of ATC and subsequently in the field of OSCC. The study of ATC was performed using an in vitro and in vivo model, investigating the main signaling pathways related to KRAS. The in vitro model was performed using different TC cell lines to study the effect of BAY-293 on the modulation of Mitogen-activated protein kinase (MAPK) pathways , apoptosis and cell migration. To confirm the in vitro mechanism and better mimic the complex tumor microenvironment, an in vivo orthotopic model of ATC was used. This involved in situ inoculation of ATC cells into the thyroid of mice, followed by treatment with BAY-293. Histological analysis and Masson's trichrome staining of mouse thyroids were performed to evaluate the effects of BAY-293 on tumor growth and progression, and Western blot analysis was used to examine markers related to KRAS/MAPK and apoptosis pathway. The results of the ATC study indicate that BAY-293, both in vitro and in vivo, effectively blocked the KRAS/MAPK/ERK pathway and β-catenin that act as essential downstream effectors for cell migration and increased the apoptotic process by slowing the progression of ATC. The study of BAY-293 in the field of OSCC was performed using an in vitro model. In the in vitro model of OSCC, BAY-293 significantly reduced the cell viability of CAL-27 cells by modulating the activation of NF-κB/IκBα pathway and the release of inflammatory mediators. In addition, BAY-293 reduced the expression of eNOS and TGFβ, two important markers of angiogenesis, and significantly increased the apoptosis pathway in OSCC cells. Overall, these results demonstrated that KRAS/SOS1 inhibition could be a promising therapeutic target for the treatment of ATC and OSCC and highlighted BAY-293 as a novel molecule that requires further research to fully evaluate its efficacy in these types of tumors.