Abstract 5500: Patient-derived organotypic cultures (PDOCs) from melanoma metastases as a precision medicine test to improve patient management
Authors: Bresin Antonella , Lotti Fiorenza , Levati Lauretta , Ferrucci Pier F. , Ricci Francesca , Scicchitano Francesco , Rocco Zorika C. Di , Russo Giandomenico , Lanfrancone Luisa 
Published: April 2023

INTRODUCTION Despite significant improvements in advanced melanoma therapy, there is still a pressing need for innovative therapies. Here, we optimized a method for testing the drug sensitivity of PDOCs and evaluated whether this preclinical model could be a valid tool for rapidly determining the patient’s tumor response profile to approved and alternative therapies.

METHODS PDOCs were generated from melanoma metastases (&gt; 60 specimens) after mechanical or enzymatic dissociation. Tissue fragments (&lt;70um) were harvested, embedded in 3D collagen beads (1.5 mg/mL type I collagen), and cultured in a 96-well plate for 6 days, maintaining tumor and stromal viability. More than 20 primary cell lines from the same samples were also stabilized. The melanoma cells or the PDOCs were left untreated or treated with the patient’s own therapy or with alternative drugs, and the efficacy of treatments was evaluated by MTT assay and flow cytometry. CD8+ T cell infiltration and cytokine secretion were also investigated.

RESULTS The first experiments were set up to validate PDOCs as predictive preclinical models of patient response to therapy. We tested approved melanoma therapies (i.e., the combination of BRAF and MEK inhibitors, or anti-PD-1 antibodies) on the same melanoma specimens at the IDI and IEO institutes. More than 10 different samples were compared, finding reproducible results between the two Institutions. Furthermore, drug response in PDOCs was comparable to the clinical response of matched patients undergoing the tested therapy, demonstrating PDOCs are reliable predictive tools. Then, we used primary cell lines to screen a pool of ten different targeted agents selected through functional screening of a bioactive library of 512 compounds on patient-derived xenografts, and based on known drug resistance mechanisms in melanoma. The three best-performing compounds were subsequently studied in PDOCs as single agents or in combination with immunotherapy. We found high heterogeneity of drug efficacy in different melanoma samples with no obvious correlation to BRAF or NRAS mutations, metastasis type, or patients’ prior therapies. Of note, in some cases, the combination with an anti-PD-1 inhibitor significantly improved the efficacy of one or more of the three drugs.

CONCLUSIONS We optimized and validated PDOCs as personalized preclinical models suitable for assessing the drug sensitivity/resistance profile of individual patient-derived melanomas. By retaining tumor stromal components and heterogeneity, PDOCs could be used to predict patients’ clinical response to currently approved agents, helping oncologists expedite decision-making when several treatment options are possible. Furthermore, the model could be used to evaluate the effectiveness of alternative treatments on tumors resistant to approved therapies, and to explore new drug combinations.

Citation Format: Antonella Bresin, Fiorenza Lotti, Lauretta Levati, Pier F. Ferrucci, Francesca Ricci, Francesco Scicchitano, Zorika C. Di Rocco, Giandomenico Russo, Luisa Lanfrancone. Patient-derived organotypic cultures (PDOCs) from melanoma metastases as a precision medicine test to improve patient management. [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 5500.