MicroRNA expression and clinical outcomes in patients treated with adjuvant chemotherapy after complete resection of non-small cell lung carcinoma

Abstract

This study determined whether expression levels of a panel of biologically relevant microRNAs can be used as prognostic or predictive biomarkers in patients who participated in the International Adjuvant Lung Cancer Trial (IALT), the largest randomized study conducted to date of adjuvant chemotherapy in patients with radically resected non-small cell lung carcinoma (NSCLC). Expression of miR-21, miR-29b, miR-34a/b/c, miR-155, and let-7a was determined by quantitative real-time PCR in formalin-fixed paraffin-embedded tumor specimens from 639 IALT patients. The prognostic and predictive values of microRNA expression for survival were studied using a Cox model, which included every factor used in the stratified randomization, clinicopathologic prognostic factors, and other factors statistically related to microRNA expression. Investigation of the expression pattern of microRNAs in situ was performed. We also analyzed the association of TP53 mutation status and miR-34a/b/c expression, epidermal growth factor receptor and KRAS mutation status, and miR-21 and Let-7a expression. Finally, the association of p16 and miR-29b expression was assessed. Overall, no significant association was found between any of the tested microRNAs and survival, with the exception of miR-21 for which a deleterious prognostic effect of lowered expression was suggested. Otherwise, no single or combinatorial microRNA expression profile predicted response to adjuvant cisplatin-based chemotherapy. Together, our results indicate that the microRNA expression patterns examined were neither predictive nor prognostic in a large patient cohort with radically resected NSCLC, randomized to receive adjuvant cisplatin-based chemotherapy versus follow-up only.

©2010 AACR.

Figures

Fig. 1

Kaplan-Meier estimates of overall survival according to miR-21 expression (A), miR-29b expression (B), miR-34a expression (C), miR-34b expression (D), miR-34c expression (E), miR-155 expression (F), Let-7a expression (G).

Fig 2. In situ hybridization for microRNAs in lung tumors

Lung tumors were hybridized with biotin-labeled microRNA (miR) probes that were detected using a biotinyl tyramide-based system and Vector NovaRed as a substrate (brown/red). Tissues were counterstained with Mayer’s hematoxylin (blue). Tissue sections were sourced from both the IALT cohort, and the University of Maryland. Representative slides with positive staining cells are shown for various cancer types, but was not limited to these specific types. Positively staining cells are shown for (A) miR-21 in adenocarcinoma, (B) miR-34a in a large cell carcinoma with neuroendocrine features, (C) miR-155 in squamous cell carcinoma (SCC), and (D) let-7a in adenocarcinoma. Staining was limited to the cytoplasm, as expected, and was diffusely localized within tumor types except for miR-155 in SCC. Mir-155 was expressed in cells on the edge of squamous cell nodules within SSCs. (E) U6 and (F) Scramble probes were used as positive and negative controls, respectively.