Enhanced glucose metabolism mediated by CD147 is associated with 18 F-FDG PET/CT imaging in lung adenocarcinoma

Abstract

Background: Lung adenocarcinoma (LUAD) is one of the most deadly thoracic tumors. Reprogrammed glycolytic metabolism is a hallmark of cancer cells and significantly affects several cellular functions. In the current study, we aimed to investigate cluster of differentiation 147 (CD147)-mediated glucose metabolic regulation in LUAD and its association with ¹⁸ F-FDG PET/CT imaging.

Methods: The expression profile and prognostic potential of CD147 in LUAD were analyzed using UALCAN and a Kaplan-Meier plotter. Tissue immunohistochemical analyses and PET metabolic parameters were used to identify the relationship between CD147 expression and reprogrammed glycolysis. The role of CD147 in glucose metabolic reprogramming was assessed by radioactive uptake of ¹⁸ F-FDG through γ-radioimmunoassays in vitro and micro-PET/CT imaging in vivo. Western blotting assays were used to determine the expression level of monocarboxylate transporter 1 (MCT1) and MCT4 in established human LUAD cell lines (ie, HCC827 and H1975) with different CD147 expression levels via lentiviral transduction.

Results: CD147 was highly expressed in LUAD. A significant positive correlation existed between CD147 expression and PET metabolic parameters(SUVmax,SUVmean, SUVpeak). CD147 could promote radioactive uptake of ¹⁸ F-FDG in vitro and in vivo, suggesting the ability of CD147 to enhance glycolytic metabolism. Furthermore, as an obligate chaperone for MCT1 and MCT4, CD147 positively correlated with MCT1 and MCT4 expression in LUAD tissues and established cell lines with different CD147 expression.

Conclusions: Our study revealed that CD147 is a promising novel target for LUAD treatment and CD147-mediated glucose metabolism demonstrated its contribution to the predictive role of ¹⁸ F-FDG PET/CT imaging for targeted therapeutic efficacy.

Keywords: 18F-FDG PET/CT imaging; CD147; glucose metabolism; lung adenocarcinoma.

Figure 1

CD147 was overexpressed in lung adenocarcinoma (LUAD), and its expression level was correlated with poor survival (a) CD147 mRNAs level in different tumors and normal tissues of multiple cancer types from TCGA database. (b) A box plot was constructed to represent the differential expression of CD147 mRNAs level between primary tumor tissues (n = 515) and normal tissues (n = 59) from LUAD patients. (c) CD147 mRNAs level was evaluated in 515 cases LUAD tissues with different disease condition (d) The relationship between CD147 expression and overall survival (OS) in lung cancer (n = 1926), described by Kaplan–Meier plotter. Expression low, high. (e) Kaplan‐Meier survival curves comparing the high and low expression of CD147 in LUAD (n = 720) which indicated that OS was significantly higher in the CD147 low expression group than in the high expression group (***P < 0.001). Expression low, high.

Figure 2

(a) Representative IHC images of CD147 and corresponding 18F‐FDG PET/CT scans. Status of CD147 on LUAD tissues was detected by IHC staining. An IHC profile was shown from three representative LUAD patients with weakly positive/negative (±, ×400, lower), positive (++, ×400, middle) and strongly positive (+++, ×400, upper) expression of CD147. Each of the corresponding 18F‐FDG‐PET/CT images revealed a solitary pulmonary lesion that was suspected to be malignant. SUVmax was 2.48 (lower), 5.70, (middle), 11.43 (upper), respectively. (b, c, d) Histograms were conducted to represent the difference in SUVmax, SUVmean and SUVpeak between different CD147 expression groups. (*P < 0.05, ***P < 0.001).

Figure 3

Different levels of CD147 expression in LUAD cell lines and the establishment of stable HCC827 and H1975 cell lines with different CD147 expression levels (a) CD147 expression level was detected by western blotting in four LUAD cell lines. (b) The CD147/GAPDH ratio simply represents the different endogenous level of CD147 in four LUAD cell lines. Statistics showed that HCC827 and H1975 cell line exhibited the highest CD147 expression. (c) Establishment of stable HCC827 cell lines (with GFP) with different levels of CD147 expression through the lentiviral transduction of CD147‐expressing lentiviral particles (CD147) and CD147‐ targeting lentiviral particles (CD147‐sh). Verification of CD147 expression was determined by western blotting. (d) Construction of stable H1975 cell lines (with GFP) with different levels of CD147 expression. Different CD147 expression levels were verified by western blotting. GFP, Green fluorescent protein(**P < 0.01, ***P < 0.001).

Figure 4

CD147 promoted 18F‐FDG uptake in human LUAD cell lines and LUAD xenograft models. (a, b) CD147 promoted 18F‐FDG uptake by both stable HCC827 and H1975 cell lines with different CD147 expression levels. 18F‐FDG was incubated in the culture media of stable HCC827 and H1975 cell lines with different levels of CD147 expression for 0.5, 1, and 2 hours. 18F‐FDG uptakes by cell lines in vitro were then measured by a γ‐radioimmunoassay. The maximal γ‐cell counts were observed with incubation for one hour. As demonstrated, HCC827‐CD147 and H1975‐CD147 cell lines with CD147 overexpression were found to be able to take up more 18F‐FDG compared to control cell lines with unaltered expression of CD147, whereas HCC827‐CD147‐sh and H1975‐CD147‐sh cell lines with decreased expression of CD147 showed attenuated uptake of 18F‐FDG compared to control counterparts. Data were from three independent tests. CD147, control, CD147‐sh (c) Representative micro‐PET/CT images of HCC827‐CD147, HCC827‐control, and HCC827‐CD147‐sh xenografts. Nude mice injected with lentiviral transduced HCC827 cell lines with different status of CD147 expression. 18F‐FDG micro‐PET/CT imaging was performed to determine the influence of CD147 on glucose uptake in vivo. The tumors were clearly visible, and more 18F‐FDG accumulation was observed in HCC827‐CD147 xenografts than in HCC827‐control and HCC827‐CD147‐sh xenografts. (d) Histograms were drawn to identify the differences existed in SUVmax for xenografts developed from lentiviral transduced HCC827 cell lines with different status of CD147 expression. As shown, the SUVmax was dramatically higher in HCC827‐CD147 xenografts than in HCC827‐control and HCC827‐CD147‐sh xenografts. Compared to the HCC827‐control xenografts, SUVmax was significantly decreased in the HCC827‐CD147‐sh xenografts. (***P < 0.001).

Figure 5

(a) Representative IHC images of CD147 and MCT1/4. (b) MCT1 and MCT4 expression levels were investigated in lentiviral transduced HCC827 cell lines by western blotting. The MCT1/GAPDH and MCT4/GAPDH ratios simply represent the level of MCT1 and MCT4 in stable HCC827 cell lines. Both ratios were considerably higher in established HCC827‐CD147 cell lines than in HCC827‐control and HCC827‐CD147‐sh cell lines. (c) Consistent with stable HCC827 cell lines, both MCT1/GAPDH and MCT4/GAPDH ratios were dramatically upregulated in the H1975‐CD147 cell line. However, both ratios were extremely reduced in the H1975‐CD147‐sh cell line. (*P < 0.05, **P < 0.01, ***P < 0.001).