BMC Cancer (Nov 2018)

Intra-patient and inter-patient comparisons of DNA damage response biomarkers in Nasopharynx Cancer (NPC): analysis of NCC0901 randomised controlled trial of induction chemotherapy in locally advanced NPC

  • Kevin Lee Min Chua,
  • Eugenia Li Ling Yeo,
  • Waseem Ahamed Shihabudeen,
  • Sze Huey Tan,
  • Than Than Shwe,
  • Enya Hui Wen Ong,
  • Paula Yeng Po Lam,
  • Khee Chee Soo,
  • Yoke Lim Soong,
  • Kam Weng Fong,
  • Terence Wee Kiat Tan,
  • Joseph Tien Seng Wee,
  • Melvin Lee Kiang Chua

DOI
https://doi.org/10.1186/s12885-018-5005-2
Journal volume & issue
Vol. 18, no. 1
pp. 1 – 11

Abstract

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Abstract Background Inter-patient heterogeneity in radiation-induced DNA damage responses is proposed to reflect intrinsic variations in tumour and normal tissue radiation sensitivity, but the prediction of phenotype by a molecular biomarker is influenced by clinical confounders and assay reproducibility. Here, we characterised the intrapatient and inter-patient heterogeneity in biomarkers of DNA damage and repair and radiation-induced apoptosis. Methods We enrolled 85 of 172 patients with locally advanced nasopharynx cancer from a randomised controlled phase II/III trial of induction chemotherapy added to chemo-radiotherapy. G0 blood lymphocytes were harvested from these patients, and irradiated with 1, 4, and 8 Gy ex vivo. DNA damage induction (1 Gy 0.5 h) and repair (4 Gy 24 h) were assessed by duplicate γH2AX foci assays in 50–100 cells. Duplicate FLICA assays performed at 48 h post-8 Gy were employed as surrogate of radiation-induced apoptosis; %FLICA-positive cells were quantified by flow cytometry. Results We observed limited intrapatient variation in γH2AX foci and %FLICA readouts; median difference of duplicate foci scores was − 0.37 (IQR = − 1.256-0.800) for 1 Gy 0.5 h and 0.09 (IQR = − 0.685-0.792) for 4 Gy 24 h; ICC of ≥0.80 was observed for duplicate %FLICA0Gy and %FLICA8Gy assays of CD4+ and CD8+ T lymphocytes. As expected, we observed wide inter-patient heterogeneity in both assays that was independent of intrapatient variation and clinical covariates, with the exception of age, which was inversely correlated with %FLICAbackground-corrected (Spearman R = − 0.406, P < 0.001 [CD4+]; R = − 0.220, P = 0.04 [CD8+]). Lastly, an exploratory case-control analysis indicates increased levels of γH2AX foci at 4 Gy 24 h in patients with severe late radiotherapy-induced xerostomia (P = 0.05). Conclusion Here, we confirmed the technical reproducibility of DNA damage response assays for clinical implementation as biomarkers of clinical radiosensitivity in nasopharynx cancer patients.

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