Abstract B122: The CD98hc oncoprotein as a target of new anticancer therapy

Among the proteins putatively interacting with PTPRJ, a tyrosine phosphatase with tumor suppressor activity, we focused on the oncoprotein CD98hc as a very interesting candidate for the development of innovative targeted drugs. In fact, CD98hc, representing the heavy chain of a transmembrane aminoacid transporter, is overexpressed in several human cancers. Furthermore, CD98hc higher expression is associated with poor prognosis in lung cancer patients. CD98hc is linked to light chains (LATs, xCT) by disulfide bridge, polar and hydrophobic interactions. The light chain confers substrate specificity, and ERK, AKT, FAK and mTOR pathways are involved in CD98hc-LATs/xCT downstream signals. Moreover, CD98hc is a coreceptor of b-integrins and it is involved in cell proliferation, migration and invasion. We identified two peptides and 15 small molecules (putatively targeting the disulfide bridge) as candidate CD98hc inhibitors by phage display and in silico screenings, respectively, and validated in vitro the binding between peptides and transmembrane fraction of CD98hc by cytofluorimetric assay. Then, we tested the capability of both types of compounds to affect cell viability and proliferation through MTT and CFSE assays, respectively. We observed that the targeting of CD98hc through both peptides and small molecules reduced cell proliferation in A549 human lung cancer cells, strongly encouraging a deeper characterization of these candidate anticancer molecules. Indeed, our next goals will be the assessment of biochemical activity of CD98hc following to its inhibition, as well as the evaluation of compounds toxicity, both in vitro and in vivo. The final aim is to identify lead compounds inhibiting CD98hc, in order to develop novel molecules to be translated in the clinical setting and to be used as monotherapy and/or in a combinatorial approaches for the treatment of cancer patients.