MiRNAs associated with time to progression in metastatic renal cell carcinoma patients treated with sunitinib

Background: Tyrosine kinase inhibitors (TKIs) are widely used in the palliative treatment of metastatic renal cell carcinoma (mRCC). TKIs inhibit multiple receptor tyrosine kinases and their main effect is mediated through the inhibition of angiogenesis. Almost all patients will sooner or later develop resistance to the anti-VEGF effect. Personalized therapy requires an effective tool for distinguishing patients according to the expected therapy outcome. MiRNAs, potent regulators of gene expression, could be suitable predictive markers. Dysregulation of miRNAs network has been linked to various diseases including RCC. Our study was focused on finding tissue miRNAs associated with time to progression (TTP) of mRCC in patients treated with sunitinib.

Material and Methods: The study was approved by the local Ethics Board and written informed consent was obtained from all patients. The screening and the validation cohort included 16, and 63 patients respectively. Response to sunitinib was assessed according to RECIST criteria after 9 months and patients were divided as follows: a) responders (CR, PR, SD), and b) non-responders (PD). Tumor tissue was provided as formalin-fixed paraffin embedded samples. Total RNA was isolated using mirVana miRNA Isolation Kit (Ambion, USA). Profiling of 667 miRNAs was conducted using TaqMan Low-Density Array (TLDA) technology. Megaplex miRNA RT primers set (Applied Biosystems, USA) were used for reverse transcription. Gene-specific primers were used in reverse transcription for qRT-PCR according to the manufacturer's protocol (Applied Biosystems). PCR reactions were run in duplicates. Expression data from TLDA were normalized using miR-625* and evaluated using Bioconductor Limma differential expression analysis. In validation cohort, expression levels of miRNAs were normalized using miR-1233 and evaluated by ROC and Kaplan–Meier analysis followed by Log-rank test (GraphPad Prism 5.03).

Results: MiRNA profiling of tumor tissue of responders (N=8) and non-responders (N=8) to sunitinib revealed 19 differentially expressed miRNAs. 6 of them (P-value <0.01: miR-155, miR-374–5p, miR-324–3p, miR-484, miR-302c, miR-888) were chosen for the verification on the independent cohort (N=63) by qRT-PCR. Kaplan–Meier analysis indicates that lower levels of miR-155 (median TTP 12.8 vs. 5.8 months, P-value <0.01) and miR-484 (median TTP 8.9 vs. 5.8 months, P-value <0.05) are associated with increased TTP in patients on sunitinib treatment.

Conclusion: Expression of miR-155 and miR-484 is associated with TTP. These miRNAs thus might be connected with sunitinib resistance. MiR-155 is a known oncogene with direct impact on angiogenesis. The role of miR-484 in mRCC remains to be clarified. Stratification of patients based on miRNA analysis could allow more personalized approach in mRCC therapy.

Supported by grant MZCR NT/13547–4/2012.

No conflict of interest.