Abstract 5993: Dissecting the role of CDK4 in liposarcoma

Abstract Background: Liposarcoma (LPS) encompass one of most common soft tissue sarcoma (STS) histological subtypes accounting for 15% of all cases. They can be divided into four entities including atypical lipomatous tumor or well-differentiated LPS (ALT/WDLPS), dedifferentiated LPS (DDLPS), myxoid LPS (MLPS) and pleomorphic LPS (PLS). Their heterogeneity is reflected in their morphology, molecular landscape, prognosis and clinical behavior. Current treatment options for localized disease include surgery, (neo)adjuvant radiotherapy and chemotherapy; for the metastatic setting chemotherapy represents the cornerstone but its role needs to be elucidated. The unavailability of predictive biomarkers makes the management of these mesenchymal diseases even more challenging. Recent evidences have shed light on the key role of cyclin-dependent kinase 4 (CDK4) in cancer cells proliferation. Methods: This study involved 21 adult patients affected by liposarcoma (n= 5 ALT/WDLPS and n= 16 DDLPS). IHC analyses of CDK4 and MDM2 were performed on FFPE surgically resected specimens by experienced sarcoma pathologists. Moreover, a patient-derived DDLPS cell line was established and pharmacological profiling was performed. Next, standard and innovative drugs currently used for LPS management were assessed in both 2D and 3D culture systems. Finally, in silico analyses based on public repositories on STS were carried out including 260 sarcoma patients. Results: IHC results highlighted an higher expression of CDK4 and MDM2 biomarkers in DDLPS compared to ALT/WDLSP. Moreover, although CDK4 and MDM2 are codified by the same genomic region, their expression did not correlate (e.g. 100% of CDK4 and 2% of MDM2 in the same patient). Therefore we hypothesized that even exhibiting a low MDM2 expression, a patient could benefit from CDK4 inhibition. Furthermore, our data showed that in DDLPS cases CDK4 expression ranged from 90% to 100% in spermatic cord, skin and abdomen while it ranged from 5% to 50% in the retroperitoneum. The above observations prompted us to hypothesize a correlation of CDK4 expression with specific anatomical sites. Moreover, pharmacological profiling showed a synergistic effect exerted by sequential treatment with palbociclib and some chemotherapeutics including trabectedin, dacarbazine, eribulin and lenvatinib. Indeed we observed a 10% increase in cell proliferation inhibition compared to standard treatment. In addition, in silico analyses revealed the role of CDK4 as negative prognostic biomarker for PFS and OS in STS. Conclusions: Our study highlighted the promising role of CDK4 in the management of LPS patients. In particular, we pointed out encouraging results of sequential treatment combining CDK4 inhibitor palbociclib and chemotherapy. Furthermore, preliminary analyses highlighted the involvement of this biomarker as a potential prognostic tool for STS. Citation Format: Silvia Vanni, Graziana Gallo, Valentina Fausti, Giacomo Miserocchi, Chiara Liverani, Chiara Spadazzi, Claudia Cocchi, Chiara Calabrese, Giovanni De Luca, Massimo Bassi, Manlio Gessaroli, Angelo Campobassi, Federica Pieri, Giorgio Ercolani, Davide Cavaliere, Lorena Gurrieri, Nada Riva, Giovanni Martinelli, Laura Mercatali, Alessandro De Vita. Dissecting the role of CDK4 in liposarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5993.