CD44: A New Prognostic Marker in Colorectal Cancer?

Cluster of differentiation 44 (CD44) is a non-kinase cell surface glycoprotein. It is overexpressed in several cell types, including cancer stem cells (CSCs). Cells overexpressing CD44 exhibit several CSC traits, such as self-renewal, epithelial-mesenchymal transition (EMT) capability, and resistance to chemo- and radiotherapy. The role of CD44 in maintaining stemness and the CSC function in tumor progression is accomplished by binding to its main ligand, hyaluronan (HA). The HA-CD44 complex activates several signaling pathways that lead to cell proliferation, adhesion, migration, and invasion. The CD44 gene regularly undergoes alternative splicing, resulting in the standard (CD44s) and variant (CD44v) isoforms. The different functional roles of CD44s and specific CD44v isoforms still need to be fully understood. The clinicopathological impact of CD44 and its isoforms in promoting tumorigenesis suggests that CD44 could be a molecular target for cancer therapy. Furthermore, the recent association observed between CD44 and KRAS-dependent carcinomas and the potential correlations between CD44 and tumor mutational burden (TMB) and microsatellite instability (MSI) open new research scenarios for developing new strategies in cancer treatment. This review summarises current research regarding the different CD44 isoform structures, their roles, and functions in supporting tumorigenesis and discusses its therapeutic implications.

Fibroblast growth factor receptors as targets for anticancer therapy in cholangiocarcinomas and urothelial carcinomas.

Cholangiocarcinomas and urothelial carcinomas are lethal tumors worldwide and only a minority of patients are eligible for surgery at diagnosis. Moreover, patients are poorly responsive to current therapeutic strategies, including chemotherapy, radiotherapy, immunotherapy, and multimodality treatments. Recently, several advances have been made in precision medicine and these results are modifying the treatment paradigm for patients diagnosed with cholangiocarcinomas and urothelial carcinoma. These histotypes exhibit a high rate of multiple fibroblast growth factor receptor (FGFR) genetic alterations and numerous preclinical and clinical studies support FGFR as a highly attractive novel therapeutic target. Moreover, identifying specific genetic alterations may predict the tumor's response to conventional and novel FGFR-targeted drugs. Recent clinical studies showed promising data for FGFR-targeted therapy in reducing tumor volume and led to the United States Food and Drug Administration (FDA) approval of, e.g., pemigatinib, infigratinib, futibatinib, and erdafitinib. Moreover, FGFR inhibitors show promising results in the first-line setting of cholangiocarcinomas and urothelial carcinomas. Pemigatinib (FIGHT-302) and futibatinib (FOENIX-CAA3) are being evaluated in phase III trials that compare these agents to current first-line gemcitabine and cisplatin in FGFR2-rearranged cholangiocarcinoma. However, complexity in targeting the FGFR signaling pathway is observed. Herein, we describe the characteristics of the FDA-approved and other investigational FGFR-targeted therapeutics, evaluate the most recent preclinical and clinical studies focusing on targeting FGFR genomic alterations in the treatment of cholangiocarcinomas and urothelial cancer, and provide insight into factors involved in response and (acquired) resistance to FGFR inhibition.