TERT promoter status and gene copy number gains: effect on TERT expression and association with prognosis in breast cancer TERT promoter status and gene copy number gains: effect on TERT expression and association with prognosis in breast cancer

Telomeres are nucleoprotein structures at the end of chromosomes which stabilize and protect them from nucleotidic degradation and end-to-end fusions. The G-rich telomeric single-stranded DNA overhang can adopt a four-stranded G-quadruplex DNA structure (G4). Stabilization of the G4 structure by binding of small molecule ligands enhances radiosensitivity of tumor cells and this combined treatment represents a novel anticancer approach. We studied the effect of the platinum-derived G4-ligand, Pt-ctpy, in association with radiation on human glioblastoma (SF763 and SF767) and non-small cell lung cancer (A549 and H1299) cells in vitro and in vivo. Treatments with submicromolar concentrations of Pt-ctpy inhibited tumor proliferation in vitro with cell cycle alterations and induction of apoptosis. Non-toxic concentrations of the ligand were then combined with ionizing radiation. Pt-ctpy radiosensitized all cell lines with dose-enhancement factors between 1.32 and 1.77. The combined treatment led to increased DNA breaks. Furthermore, a significant radiosensitizing effect of Pt-ctpy in mice xenografted with glioblastoma SF763 cells was shown by delayed tumor growth and improved survival. Pt-ctpy can act in synergy with radiation for efficient killing of cancer cells at concentrations at which it has no obvious toxicity per se, opening perspectives for future therapeutic applications.

Dysfunctional telomeres and DNA damage repair (DDR) play important roles in cancer progression. Studies have reported correlations between these factors and tumour aggressiveness and clinical outcome in breast cancer. We studied the characteristics of telomeres and expression of ERCC1, a protein involved in a number of DNA repair pathways and in telomere homeostasis, to assess their prognostic value, alone or in combination, in 90 residual breast tumours after treatment with neoadjuvant chemotherapy (NCT). ERCC1 status was investigated at different molecular levels (protein and gene expression and gene copy‐number variations) by immunohistochemistry, qRT‐PCR and quantitative multiplex fluorescent‐PCR (QMF‐PCR). A comprehensive analysis of telomere characteristics was performed using qPCR for telomere length and qRT‐PCR for telomerase (hTERT), tankyrase 1 (TNKS) and shelterin complex (TRF1, TRF2, POT1, TPP1, RAP1 and TIN2) gene expression. Short telomeres, high hTERT and TNKS expression and low ERCC1 protein expression were independently associated with worse survival outcome. Interestingly, ERCC1 gains and losses correlated with worse disease‐free (p = 0.026) and overall (p = 0.043) survival as compared to survival of patients with normal gene copy‐numbers. Unsupervised hierarchical clustering of all ERCC1 and telomere parameters identified four subgroups with distinct prognosis. In particular, a cluster combining low ERCC1, ERCC1 gene alterations, dysfunctional telomeres and high hTERT and a cluster with high TNKS and shelterin expression correlated with poor disease‐free (HR= 5.41, p= 0.0044) and overall survival (HR= 6.01, p= 0.0023) irrespective of tumour stage and grade. This comprehensive study demonstrates that telomere dysfunction and DDR can contribute synergistically to tumour progression and chemoresistance. These parameters are predictors of clinical outcome in breast cancer patients treated with NCT and could be useful clinically as prognostic biomarkers to tailor adjuvant chemotherapy post‐NCT.

// <![CDATA[ $('.header-date').hide();$('#titleAuthors').hide();$('#abstractHeader').hide(); // ]]> Romain Guièze1, *, Mélanie Pages2, *, Lauren Véronèse3, Patricia Combes3, Richard Lemal1, Mathilde Gay-bellile3, Martine Chauvet4, Mary Callanan4, Fabrice Kwiatkowski5, Bruno Pereira6, Philippe Vago3, Jacques-Olivier Bay1, Olivier Tournilhac1, Andreï Tchirkov3 1CHU Clermont-Ferrand, Hématologie Clinique, Clermont-Ferrand, F-63003; EA 7283 CREaT, Université d’Auvergne Clermont-Ferrand, France 2Department de Neuropathologie, Hôpital Sainte-Anne, Paris, France; Université Paris Descartes, Paris, France 3Univ Clermont 1, UFR Médecine, Cytologie Histologie Embryologie Cytogénétique, Clermont-Ferrand, F-63001; CHU Clermont-Ferrand, Cytogénétique Médicale, Clermont-Ferrand, F-63003; EA 4677 ERTICa, Université d’Auvergne, Clermont-Ferrand, France 4Inserm U823, Institut Albert Bonniot & Université Joseph Fourier, Grenoble, France; CHU Grenoble, Laboratoire de Génétique Onco-hématologique, Grenoble, France 5Centre Jean Perrin, Clermont-Ferrand, France; EA 4677 ERTICa, Université d’Auvergne, Clermont-Ferrand, France 6Direction de la Recherche Clinique et de l’Innovation, Département de Biostatistiques, CHU Clermont-Ferrand, Clermont-Ferrand, France *These authors have contributed equally to this work Correspondence to: Andreï Tchirkov, email: atchirkov@chu-clermontferrand.fr Keywords: chronic lymphocytic leukemia, TP53, telomere, hTERT, shelterin Received: April 13, 2016 Accepted: July 10, 2016 Published: July 29, 2016