Assessing the function of homologous recombination DNA repair in malignant pleural effusion (MPE) samples

Our plain-English summary of Assessing the function of homologous recombination DNA repair in malignant pleural effusion (MPE) samples, by M.J. Patterson, R.E. Sutton, I. Forrest, et al (British Journal of Cancer, 2014).

The study

• Authors: M.J. Patterson, R.E. Sutton, I. Forrest, R. Sharrock, M. Lane, A. Kaufmann, R. O'Donnell, R.J. Edmondson, B.T. Wilson, N.J. Curtin
• Journal: British Journal of Cancer
• Published: 2014;111(1):94-100
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Patients with malignant pleural effusions (MPEs) generally have advanced disease with poor survival and few therapeutic options. Cells within MPEs may be used to stratify patients for targeted therapy. Targeted therapy with poly(ADP ribose) polymerase inhibitors (PARPi) depends on identifying homologous recombination DNA repair (HRR)-defective cancer cells. We aimed to determine the feasibility of assaying HRR status in MPE cells.

Methods: A total of 15 MPE samples were collected from consenting patients with non-small-cell lung cancer (NSCLC), mesothelioma and ovarian and breast cancer. Primary cultures were confirmed as epithelial by pancytokeratin, and HRR status was determined by the detection of γH2AX and RAD51 foci following a 24-h exposure to rucaparib, by immunofluorescence microscopy. Massively parallel next-generation sequencing of DNA repair genes was performed on cultured MPE cells.

Results: From 15 MPE samples, 13 cultures were successfully established, with HRR function successfully determined in 12 cultures. Four samples - three NSCLC and one mesothelioma - were HRR defective and eight samples - one NSCLC, one mesothelioma, one sarcomatoid, one breast and four ovarian cancers - were HRR functional. No mutations in DNA repair genes were associated with HRR status, but there was probable loss of heterozygosity of FANCG, RPA1 and PARP1.

Conclusions: HRR function can be successfully detected in MPE cells demonstrating the potential to stratify patients for targeted therapy with PARPi.

In plain English

This UK laboratory feasibility study tested whether cancer cells in fluid around the lungs (malignant pleural effusions) could be checked for a DNA repair process called homologous recombination repair (HRR). Cancers with faulty HRR may respond to drugs called PARP inhibitors. The authors collected 15 samples from patients with non-small-cell lung cancer (NSCLC), mesothelioma, ovarian and breast cancer. Cells grew from 13 samples; two ovarian samples were contaminated. After 24 hours' treatment with the PARP inhibitor rucaparib, HRR status was determined for 12 cultures. Four (three NSCLC, one mesothelioma) were HRR defective. Eight were HRR competent: four ovarian, one NSCLC, one mesothelioma, one breast, and one tumour recorded as sarcomatoid lung carcinoma or possibly sarcomatoid mesothelioma. Survival did not differ significantly between the groups. Sequencing five cultures found no trends of genetic changes. However, probable loss of heterozygosity of PARP1, RPA1 and FANCG appeared only in HRR-defective cultures, and the authors called its significance unclear. The authors concluded that HRR function can be detected in these cells, and they noted their small sample size. The article does not discuss asbestos exposure.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory feasibility study on cells grown from patients' malignant pleural effusion samples, with immunofluorescence testing of DNA repair and gene sequencing
• Who was studied: 15 malignant pleural effusion samples from cancer patients undergoing routine thoracocentesis at hospitals in Newcastle upon Tyne and Gateshead, UK. The cancers were NSCLC, mesothelioma, ovarian and breast cancer, plus one tumour recorded as sarcomatoid lung carcinoma or possibly sarcomatoid mesothelioma. HRR status was determined for 12 patients.
• Exposure: No asbestos or occupational exposure was studied. In the laboratory, cultured cells were treated with the PARP inhibitor rucaparib for 24 hours to induce DNA damage and test HRR function.
• Main results:
  • Cultures were established from 13 of 15 samples. Two ovarian cancer samples were contaminated and not assessed further.
  • DNA damage was not induced in one ovarian cancer culture (PPE011), so its HRR status could not be assessed.
  • Four cultures were HRR defective: three NSCLC and one mesothelioma.
  • Eight cultures were HRR competent: one NSCLC (PPE012), one mesothelioma, one sarcomatoid tumour, one breast cancer and four ovarian cancers. The tables record the sarcomatoid tumour as sarcomatoid lung carcinoma or possibly sarcomatoid mesothelioma.
  • Overall survival did not differ significantly between patients whose cells were HRR competent and those whose cells were HRR dysfunctional.
  • None of the NSCLC patients were fit enough for platinum-based therapy. The patient with HRR-defective mesothelioma received platinum-based therapy.
  • Sequencing of DNA repair genes in five cultures (three HRR competent, two HRR dysfunctional) found no trends of genetic aberrations.
  • Probable loss of heterozygosity of PARP1, RPA1 and FANCG was seen only in the HRR-dysfunctional cultures. The authors said its functional significance is unclear.
• The authors' conclusion: The authors concluded that HRR function can be detected in cells from malignant pleural effusions, which shows potential for selecting patients for PARP inhibitor therapy. They proposed extending the study to a larger group of patients.
• Limitations the authors state:
  • The small sample size may explain why none of the ovarian cancer cultures were HRR defective.
  • The assay may have underestimated HRR defects, because it does not detect defects that occur after RAD51 foci form.
  • The cells grew too poorly to test their sensitivity to PARP inhibitors directly in the laboratory.
  • The small sample size prevented confident detection of genetic patterns.
  • Culturing mixed tumour cells may have masked genetic signatures.
  • The sequencing platform could not evaluate gene copy number.
  • Only one mesothelioma patient was treated, so it could not be established whether that patient's response to therapy was due to an HRR defect.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Effusion, Targeted Therapy, Lung Cancer, Mesothelioma, Next-Generation Sequencing (NGS), Sarcomatoid, Ovarian Cancer.

Related studies

• Gene expression profiling of homologous recombination repair pathway indicates susceptibility for olaparib treatment in malignant pleural mesothelioma in vitro — S. Borchert, M. Wessolly, et al. (2019)
• The Association of BAP1 Loss-of-Function With the Defect in Homologous Recombination Repair and Sensitivity to PARP-Targeted Therapy — H. Yang, D. Xu, et al. (2020)
• Exploring the Frequency of Homologous Recombination DNA Repair Dysfunction in Multiple Cancer Types — L. Gentles, B. Goranov, et al. (2019)
• High frequency of pathogenic germline variants within homologous recombination repair in patients with advanced cancer — B. Bertelsen, I.V. Tuxen, et al. (2019)
• Defining the minimal important difference for the visual analogue scale assessing dyspnea in patients with malignant pleural effusions — E.K. Mishra, J.P. Corcoran, et al. (2015)
• Chrysotile asbestos fibers mediate homologous recombination in Rat2 lambda fibroblasts: implications for carcinogenesis — K. Lezon-Geyda, C.M. Jaime, et al. (1996)

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