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. 2022 Apr 15;82(8):1646-1657.
doi: 10.1158/0008-5472.CAN-21-2409.

Preclinical In Vivo Validation of the RAD51 Test for Identification of Homologous Recombination-Deficient Tumors and Patient Stratification

Benedetta Pellegrino #  1   2 , Andrea Herencia-Ropero #  3   4 , Alba Llop-Guevara  3 , Flaminia Pedretti  3   4 , Alejandro Moles-Fernández  5 , Cristina Viaplana  6 , Guillermo Villacampa  6 , Marta Guzmán  3 , Olga Rodríguez  3 , Judit Grueso  3 , Jose Jiménez  7 , Enrique J Arenas  8   9 , Andrea Degasperi  10   11 , João M L Dias  10   11 , Josep V Forment  12 , Mark J O'Connor  13 , Olivier Déas  14 , Stefano Cairo  14 , Yinghui Zhou  15 , Antonino Musolino  1   2 , Carlos Caldas  16   17 , Serena Nik-Zainal  10   11 , Robert B Clarke  18 , Paolo Nuciforo  7 , Orland Díez  5   19 , Xavier Serres-Créixams  20 , Vicente Peg  21 , Martín Espinosa-Bravo  22 , Teresa Macarulla  23   24 , Ana Oaknin  24   25 , Joaquin Mateo  24   26 , Joaquín Arribas  4   8   9   27   28 , Rodrigo Dienstmann  6 , Meritxell Bellet  24   29 , Mafalda Oliveira  24   29 , Cristina Saura  24   29 , Sara Gutiérrez-Enríquez  5 , Judith Balmaña  5   24 , Violeta Serra  3   9
Affiliations

Preclinical In Vivo Validation of the RAD51 Test for Identification of Homologous Recombination-Deficient Tumors and Patient Stratification

Benedetta Pellegrino et al. Cancer Res. .

Abstract

PARP inhibitors (PARPi) are approved drugs for platinum-sensitive, high-grade serous ovarian cancer (HGSOC) and for breast, prostate, and pancreatic cancers (PaC) harboring genetic alterations impairing homologous recombination repair (HRR). Detection of nuclear RAD51 foci in tumor cells is a marker of HRR functionality, and we previously established a test to detect RAD51 nuclear foci. Here, we aimed to validate the RAD51 score cut off and compare the performance of this test to other HRR deficiency (HRD) detection methods. Laboratory models from BRCA1/BRCA2-associated breast cancer, HGSOC, and PaC were developed and evaluated for their response to PARPi and cisplatin. HRD in these models and patient samples was evaluated by DNA sequencing of HRR genes, genomic HRD tests, and RAD51 foci detection. We established patient-derived xenograft models from breast cancer (n = 103), HGSOC (n = 4), and PaC (n = 2) that recapitulated patient HRD status and treatment response. The RAD51 test showed higher accuracy than HRR gene mutations and genomic HRD analysis for predicting PARPi response (95%, 67%, and 71%, respectively). RAD51 detection captured dynamic changes in HRR status upon acquisition of PARPi resistance. The accuracy of the RAD51 test was similar to HRR gene mutations for predicting platinum response. The predefined RAD51 score cut off was validated, and the high predictive value of the RAD51 test in preclinical models was confirmed. These results collectively support pursuing clinical assessment of the RAD51 test in patient samples from randomized trials testing PARPi or platinum-based therapies.

Significance: This work demonstrates the high accuracy of a histopathology-based test based on the detection of RAD51 nuclear foci in predicting response to PARPi and cisplatin.

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Conflict of interest statement

Conflict of interest statement

B.P. received honoraria from Novartis and BMS. V.S. received research funds from AstraZeneca and Tesaro, and honoraria from Abbie. J.B. received honoraria and travel money from AstraZeneca and Pfizer. V.S., J.B. and A.L.G. are named as inventors for patent PCT/EP2018/086759 (WO2019122411A1). S.C. is employee of XenTech. M.O.C, J.V.F are employees and shareholders of AstraZeneca. Y.Z. is employee from Tesaro. V.P. has received fees as consultant, participated in advisory boards or received travel grants from Roche, Sysmex, MSD, AstraZeneca, Bayer and Exact Sciences. M.O. received research support from AstraZeneca, Philips Healthcare, Genentech, Roche, Novartis, Immunomedics, Seattle Genetics, GSK, Boehringer-Ingelheim, PUMA Biotechnology, Zenith Epigenetics. She has received fees as consultant from Roche, Seattle Genetics, GSK, PUMA Biotechnology, AstraZeneca, and received honoraria from Roche, Seattle Genetics, Novartis, Guardant Health and Pfizer, as well as travel money from Roche, Pierre-Fabre, Novartis and Eisai. She is member of the SOLTI Breast Cancer Research Executive Board and Scientific Committee. J.M. served on advisory boards from Amgen, AstraZeneca, Clovis Oncology, Janssen, MSD, Pfizer and Roche and received research funding from AstraZeneca and Pfizer Oncology (not related to this work). A.M. reports grants and other from Eisai Co., Ltd; grants and personal fees from Roche; personal fees from MacroGenics; personal fees from Merck; grants and personal fees from Lilly; grants from Pfizer, outside the submitted work. T.M. received honoraria as consultant/advisory with Amgen, Baxter, Celgene, Incyte, Q&D Therapeutics, Serviere, Shire; research funding from AstraZeneca, BeiGene, Celgene. M.B. received honoraria as advisory/ conferences with Pfizer, Lilly, Novartis and travel expenses with Pfizer.

Figures

Figure 1
Figure 1. Establishing a biobank of patient-derived laboratory models.
Study design depicting the generation of PDX from BC, HGSOC and PaC, and PDC from BC. PDX (n=109) were established from patient tumor samples and PDC (n=14) were generated from the corresponding PDX.
Figure 2
Figure 2. Antitumor activity of PARPi in PDX.
A) Waterfall plot showing the best response to the PARPi olaparib or niraparib in 109 PDX, as percentage of tumor volume change, compared to the tumor volume on day 1. +20%, −30%, -95% are marked by dotted lines to indicate the range of PD, SD, PR, CR, respectively. The legend summarizes the RAD51 score (A), the genomic HRD score (B) (based on Myriad myChoice® or HRDetect) and (C) the tumor type. B) Pie charts indicating the distribution of HRR functional status and HRR alterations in 96 PDX (excluding models of acquired resistance). C) Pie charts indicating the distribution of PARPi resistance mechanisms in 69 HRR-altered tumors (including models of acquired resistance).
Figure 3
Figure 3. RAD51 functional assay predicts PARPi response in PDX.
A) Genomic HRD score in PARPi-sensitive and resistant models (n=41), measured with Myriad myChoice®. B) Comparison of the RAD51 score with the genomic HRD score as in panel B (n=41). C) Distribution of the RAD51 score in relationship to PARPi response (n=109). D) Comparison of ROC curves for the RAD51 score and Myriad myChoice® score for PARPi response in PDX (n=41).
Figure 4
Figure 4. Antitumor activity of cisplatin in PDX.
A) Waterfall plot showing the best response to cisplatin in 56 PDX, as the percentage of tumor volume change compared to the tumor volume on day 1. +20%, −30%, -95% are marked by dotted lines to indicate the range of PD, SD, PR, CR, respectively. B) Distribution of the RAD51 score in platinum-sensitive and resistant models (n=56).
Figure 5
Figure 5. Homologous recombination repair functionality and PARPi sensitivity is concordant in patient, PDX and PDC.
A) RAD51 scores in PDX and in patient’s tumor samples concurrent to the PDX establishment. B) RAD51 in PDX and corresponding PDC treated with PARPi or vehicle. C) Representation of the logarithm of the half maximal inhibitory concentration (IC50) of PDCs treated with olaparib in comparison to the in vivo sensitivity. D) Bright-field microscopic images showing one PARPi-sensitive model (PDC405) and one PARPi-resistant model (PDC270) untreated (control) and treated with olaparib 1 µM for 14 days.
See this image and copyright information in PMC

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