Comment on prognostic and therapeutic implications of mTORC2 and rictor expression in human breast cancer

Abstract

We have read with the interest the article by Haiyan Li et al. [1], in which the authors reported that targeting of mTORC2 but not mTORC1 efficiently prevented breast cancer cell migration in breast cancer cell lines and xenografts. We have recently investigated the mRNA expression of mTORC1, Raptor and Rictor (unpublished data) in a cohort of 150 breast cancer patient, patients regarding whom we have published extensively in the past. Breast cancer specimens and normal tissues (n = 31) underwent reverse transcription and quantitative PCR of cDNA using Amplifluor technology. Transcript levels were correlated with clinicopathological data. The median follow-up for this cohort is 10 years [2]. We found that Rictor expression was inversely related to the Nottingham Prognostic Index (NPI 1 vs. 2: p = 0.03) and tumour grade (grade 1 vs. 3: p = 0.01) and was associated with better overall (p = 0.037) and disease-free survival (p = 0.048). Our observation suggests that the mTORC2 core protein is a favourable biological marker in human breast cancer and therefore caution should be exercised in developing strategies to knock down this protein in human breast cancer.