The FOXC1/FBP1 signaling axis promotes colorectal cancer proliferation by enhancing the Warburg effect

Abstract

Aberrant expression of Forkhead box (FOX) transcription factors plays vital roles in carcinogenesis. However, the function of the FOX family member FOXC1 in maintenance of colorectal cancer (CRC) malignancy is unknown. Herein, FOXC1 expression in CRC specimens in The Cancer Genome Atlas (TCGA) cohort was analyzed and validated using immunohistochemistry with a tissue microarray. The effect of FOXC1 expression on proliferation of and glycolysis in CRC cells was assessed by altering its expression in vitro and in vivo. Mechanistic investigation was carried out using cell and molecular biological approaches. Our results showed that FOXC1 expression was higher in CRC specimens than in adjacent benign tissue specimens. Univariate survival analyses of the patients from whom the study specimens were obtained, and validated cohorts indicated that ectopic FOXC1 expression was significantly correlated with shortened survival. Silencing FOXC1 expression in CRC cells inhibited their proliferation and colony formation and decreased their glucose consumption and lactate production. In contrast, FOXC1 overexpression had the opposite effect. Furthermore, increased expression of FOXC1 downregulated that of a key glycolytic enzyme, fructose-1,6-bisphosphatase 1 (FBP1). Mechanistically, FOXC1 bound directly to the promoter regions of the FBP1 gene and negatively regulated its transcriptional activity. Collectively, aberrant FBP1 expression contributed to CRC tumorigenicity, and decreased FBP1 expression coupled with increased FOXC1 expression provided better prognostic information than did FOXC1 expression alone. Therefore, the FOXC1/FBP1 axis induces CRC cell proliferation, reprograms metabolism in CRCs, and constitutes potential prognostic predictors and therapeutic targets for CRC.

S100A4 promotes colorectal carcinoma growth by enhancing aerobic glycolysis

“…IHC study was used to explore S100A4 expression in patients as previously described [8] . Primary anti-S100A4 antibody (ab124805, 1:1000; Abcam) and goat anti-rabbit Envision System Plus-HRP (Dako Cytomation) were used for the study.…”

“…Fast Real-Time PCR System (Applied Biosystems, Foster City, CA, USA) as previous described [8,19] . All primers were listed in Table 1.β-actin was used as an internal control.…”

“…Standard Western blotting was carried out as previous described [8,20] . Primary antibodies anti-S100A4 (ab124805, 1:1000; Abcam), or anti-β-actin (ab133626, 1:5000; Abcam) and secondary antibodies (anti-rabbit IgG; Cell Signaling Technology, Danvers, MA, USA) were used.…”

“…The glucose assay kit (BioVision, Milpitas, CA, USA) was used to detect relative glucose uptake and lactate production among different S100A4 expression groups in CRC cells. All reactions were 5 performed in triplicate as described previously [8] .…”

“…Because it is closely related with increased progression and metastasis abilities of cancer, aerobic glycolysis is one of the basic characteristics of invasive tumors [4,5] . Recently, studies have revealed that genetic or epigenetic changes in oncogenes or tumor suppressors lead to activation of glycolysis, as most glycolytic enzymes are regulated by oncogenes or tumor suppressors such as hypoxia inducible factor (HIF) [6] , Myc [7] , FOXC1 [8] , FOXM1 [9] , Gas1 [5] , et al…”