Introduction

Our studies aim to recover clear cytoplasm in renal cell carcinoma cell lines by inducing adipogenic transdifferentiation, and to determine the effect of such a change in cell activity.

Methods

An increase in the clear cytoplasm caused using adipogenic induction media (Lonza) in Caki-1 and Caki-2 cells. Human PCR array (Qiagen) was conducted for comparison of gene expressions which are related to adipogenesis and mitochondria. Western blotting and confocal microscopy were utilized to observe the protein expressions for mitochondria biogenesis. JC-1 dye staining (Cayman) to measure mitochondrial membrane potential was performed to observe mitochondrial function.

Results

Clear cytoplasm was found to increase more in Caki-1 cells than in Caki-2. The increases of clear cytoplasm in Caki-1 cells were induced up-regulation of adipogenesis-related genes. In particular, Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1?) which promotes mitochondrial biogenesis demonstrated an 11-fold increase (Fig. 1A). This up-regulation of PGC1? genes led increases in genes of voltage-dependent anion channels and cytochrome C oxidase subunit IV, ultimately promoting mitochondrial biogenesis (Fig. 1B, C). Also, in Caki-1 cells with increased clear cytoplasm, a mitochondrial healthy state was maintained with no impact on membrane potential, which is a significant role of mitochondria for cell’s homeostasis (Fig. 2A). Such activation of PGC1? was found to be caused by increased phosphorylation of AMP-activated protein kinase (AMPK) (Fig. 2B, C).

Conclusions

We demonstrated that morphologic characteristics of ccRCC could be recovered in the renal cell carcinoma cell line by increasing clear cytoplasm using adipogenic induction. This activates the AMPK-PGC1? pathway and promotes mitochondria biogenesis with no impact on membrane potential, resulting in mitochondria being observed in a healthy state. Progression of malignant differentiation in renal cell carcinoma resulted in a marked decrease in the number and function of mitochondria. This study is expected to provide valuable clues in characterizing and treating the progression of renal cell carcinoma.

Funding

none