Login to Access Video or Poster Abstract: MP39-19
Sources of Funding: Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number T32GM088129. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Introduction

When grown under stressed conditions, a subset of neoplastic cells can undergo cell-to-cell trafficking of mitochondria through dynamic structures termed tunneling nanotubes. This horizontal mitochondrial transfer (HMT) is a relatively newly described phenomenon that may contribute to chemotherapeutic resistance in several non-urologic cancers. Since HMT might represent a novel mechanism of acquired chemoresistance in renal cell carcinoma (RCC), we sought to determine if HMT occurs in response to treatment with Sunitinib, a first line chemotherapeutic agent.

Methods

RCC cell lines (A498 and 786-O) were differentially labeled by lentiviral transduction of cytoplasm-localizing enhanced green fluorescent protein (EGFP) or mitochondria-localizing mCherry. Mitochondrial localization of mCherry (mito-mCherry) was achieved by tagging the fluorescent protein with the cyclooxygenase-8 mitochondria targeting sequence. Differentially labeled RCC cells were cultured at a 1:1 ratio and were treated with sunitinib (0uM, 1.25uM, 2.5um, 5uM, 10uM, and 20uM) for 24 hours. HMT was quantified by flow cytometry and visualized by deconvolution microscopy.

Results

HMT occurred between differentially labeled RCC cells. Co-culture of mito-mCherry A498 cells with EGFP+ A498, 786-O, and ACHN cells demonstrated mitochondrial transfer at all concentrations of sunitinib tested. 2.4% of EGFP+ A498 cells received mCherry+ mitochondria in co-culture at 0uM of sunitinib. Mitochondrial transfer was enhanced by sunitinib treatment at all doses tested (e.g. 4.26% at 10uM sunitinib). This phenomenon was not cell line specific as EGFP labeled 786-O cells also acquired mCherry+ mitochondria (8.3%). Deconvolution microscopy of fixed co-cultured cells demonstrated mCherry+ mitochondria within EGFP+ 786-O cells.

Conclusions

Here we demonstrate for the first time that sunitinib exposure potentiates cell-to-cell transfer of mitochondria in kidney cancer cell lines. The biologic significance of this process in vivo remains to be determined. Our hypothesis is that HMT may contribute to clinically relevant acquired chemoresistance in RCC and experiments are under way to explore this possibility further.

Funding

Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number T32GM088129. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.