DNA Damage and Repair Biomarkers in Cervical Cancer Patients Treated with Neoadjuvant Chemotherapy: An Exploratory Analysis.

Patrizia Vici,Enrico Vizza,Maddalena Barba,Luigi Di Lauro,Cristina Vincenzoni,Simonetta Buglioni,Luciano Mariani,Teresa Gamucci,Monica Bartucci,Giuseppe Sanguineti,Ilio Vitale,Mariantonia Carosi,Barbara Antoniani,Angiolo Gadducci,Laura Pizzuti,Francesca Sperati,Irene Terrenato,Rosanna Dattilo,Marcella Mottolese,Domenico Sergi,Ruggero De Maria,Marcello Maugeri‐Saccà

doi:10.1371/journal.pone.0149872

Abstract

Cervical cancer cells commonly harbour a defective G1/S checkpoint owing to the interaction of viral oncoproteins with p53 and retinoblastoma protein. The activation of the G2/M checkpoint may thus become essential for protecting cancer cells from genotoxic insults, such as chemotherapy. In 52 cervical cancer patients treated with neoadjuvant chemotherapy, we investigated whether the levels of phosphorylated Wee1 (pWee1), a key G2/M checkpoint kinase, and γ-H2AX, a marker of DNA double-strand breaks, discriminated between patients with a pathological complete response (pCR) and those with residual disease. We also tested the association between pWee1 and phosphorylated Chk1 (pChk1), a kinase acting upstream Wee1 in the G2/M checkpoint pathway. pWee1, γ-H2AX and pChk1 were retrospectively assessed in diagnostic biopsies by immunohistochemistry. The degrees of pWee1 and pChk1 expression were defined using three different classification methods, i.e., staining intensity, Allred score, and a multiplicative score. γ-H2AX was analyzed both as continuous and categorical variable. Irrespective of the classification used, elevated levels of pWee1 and γ-H2AX were significantly associated with a lower rate of pCR. In univariate and multivariate analyses, pWee1 and γ-H2AX were both associated with reduced pCR. Internal validation conducted through a re-sampling without replacement procedure confirmed the robustness of the multivariate model. Finally, we found a significant association between pWee1 and pChk1. The message conveyed by the present analysis is that biomarkers of DNA damage and repair may predict the efficacy of neoadjuvant chemotherapy in cervical cancer. Further studies are warranted to prospectively validate these encouraging findings.

Highlights

Eukaryotic cells are constantly exposed to endogenous and exogenous sources of DNA damage
The ataxia telangiectasia and Rad3-related protein (ATR)-Checkpoint kinase 1 (Chk1)-Wee1-like protein kinase (Wee1) cascade represents the core of the G2/M checkpoint, whose activation leads to the inhibition of the cyclin-dependent kinase 1 and culminates into checkpoint-mediated cell cycle arrest [3]
All the pre-chemotherapy samples, consisting in diagnostic biopsies, were examined for phosphorylated Wee1 (pWee1) and γ-H2AX, whereas phosphorylated Chk1 (pChk1) data were available for 37 samples

Summary

Introduction

Eukaryotic cells are constantly exposed to endogenous and exogenous sources of DNA damage. A common trait to a variety of tumors is the defective nature of the G1/S-phase checkpoint, stemming from mutational or functional inactivation of p53 or retinoblastoma protein (pRb) [3] When this occurs, cancer cells become extremely dependent on the G2/M checkpoint for cell cycle arrest and DNA repair [3]. The ataxia telangiectasia and Rad3-related protein (ATR)-Checkpoint kinase 1 (Chk1)-Wee1-like protein kinase (Wee1) cascade represents the core of the G2/M checkpoint, whose activation leads to the inhibition of the cyclin-dependent kinase 1 and culminates into checkpoint-mediated cell cycle arrest [3] In such a manner, cancer cells have the time to correct chemotherapy-induced DNA lesions, avoiding entry into a lethal mitosis known as mitotic catastrophe [4]. When G1/S-phase checkpoint-defective cells are exposed to chemotherapeutics, the concomitant pharmacological inhibition of G2/M checkpoint kinases is deleterious for cell fitness [3]

Methods

Results

Conclusion