MYC oncogene overexpression drives renal cell carcinoma in a mouse model through glutamine metabolism

Abstract

The MYC oncogene is frequently mutated and overexpressed in human renal cell carcinoma (RCC). However, there have been no studies on the causative role of MYC or any other oncogene in the initiation or maintenance of kidney tumorigenesis. Here, we show through a conditional transgenic mouse model that the MYC oncogene, but not the RAS oncogene, initiates and maintains RCC. Desorption electrospray ionization-mass-spectrometric imaging was used to obtain chemical maps of metabolites and lipids in the mouse RCC samples. Gene expression analysis revealed that the mouse tumors mimicked human RCC. The data suggested that MYC-induced RCC up-regulated the glutaminolytic pathway instead of the glycolytic pathway. The pharmacologic inhibition of glutamine metabolism with bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide impeded MYC-mediated RCC tumor progression. Our studies demonstrate that MYC overexpression causes RCC and points to the inhibition of glutamine metabolism as a potential therapeutic approach for the treatment of this disease.

Keywords: MYC oncogene; desorption electrospray ionization mass spectrometry imaging; glutamine metabolism; renal cell carcinoma.

Fig. 1.

MYC but not RAS initiates renal tumorigenesis. (A) Transgenic mice with the γ-glutamyl transferase (GGT) promoter driving the tetracycline transactivator protein (tTA) and MYC under the control of the tetracycline-responsive element generates MYC-GGT-tTA mice. (B) Kaplan–Meier overall survival analysis of mice with MYC (n = 27) or K-RAS (n = 7) transgene. ON indicates activated oncogenes, and OFF indicates oncogene was never activated. (C) Gross anatomy of a MYC-GGT-tTA kidney after 4 wk of MYC activation compared with control where MYC remain inactivated. (D) Weekly serial H&E and MYC IHC of kidney sections following MYC activation. (E) Representative IHC and immunofluorescence images showing protein expression and histological changes upon MYC activation and inactivation for 10 d. For all quantification, n = 3 mice were examined at each time point.

Fig. 2.

DESI-MSI of MYC-induced RCC shows specific lipid signature. Representative DESI-MS ion images of cross-sections of control kidney, 2-wk MYC ON kidney, 4-wk MYC ON kidney, and 4-wk MYC OFF kidney, which were analyzed concomitantly, are shown. Images display the 2D distribution of m/z 303.2309, m/z 327.2308, m/z 750.5393, m/z 771.5161, m/z 773.5344, m/z 775.5510, m/z 817.5034, m/z 819.5196, m/z 841.5037, m/z 865.5021, m/z 885.5432, m/z 867.5218, m/z 818.6018, and m/z 913.4865. The molecular identification of the ions are shown within each panel. The bottom right panel shows an optical image of the tissue sections that were H&E stained after DESI-MSI.

Fig. 3.

Glutaminolysis pathway is up-regulated in MYC-induced renal adenocarcinoma. (A) IHC showing glutaminase 1 and 2, hexokinase 1, and LDHA expression in normal kidneys (control) and kidneys that have MYC activated for 3 wk. (B) Representative DESI-MS ion images of glutamate and α-ketoglutarate at 2-wk MYC activation compared with control. H&E was performed on the same section following DESI-MSI.

Fig. 4.

Inhibition of glutaminase impedes MYC-induced renal tumorigenesis in vivo. (A) Representation of weekly MRI scans of a BPTES-treated mouse and a DMSO-treated mouse over 2 wk. (B) Percent area growth derived from MRI of tumors undergoing BPTES (n = 8) or DMSO (n = 8) treatment. (C) Final weight of kidneys treated with BPTES (n = 14), FX-11 (n = 12), or DMSO (n = 18) after 4 wk of MYC activation compared with MYC inactivation.

Fig. 5.

MYC and glutaminase are overexpressed in human RCC. (A) Quantification of IHC staining of glutaminase (GLS) (black bars) and MYC (gray bars) in clear-cell RCC (ccRCC) and collecting-duct RCC (cdRCC) human samples. (B) Representative GLS and MYC staining in ccRCC and cdRCC human samples.