HIF-Dependent CKB Expression Promotes Breast Cancer Metastasis, Whereas Cyclocreatine Therapy Impairs Cellular Invasion and Improves Chemotherapy Efficacy

Abstract

The oxygen-responsive hypoxia inducible factor (HIF)-1 promotes several steps of the metastatic cascade. A hypoxic gene signature is enriched in triple-negative breast cancers (TNBCs) and is correlated with poor patient survival. Inhibiting the HIF transcription factors with small molecules is challenging; therefore, we sought to identify genes downstream of HIF-1 that could be targeted to block invasion and metastasis. Creatine kinase brain isoform (CKB) was identified as a highly differentially expressed gene in a screen of HIF-1 wild type and knockout mammary tumor cells derived from a transgenic model of metastatic breast cancer. CKB is a cytosolic enzyme that reversibly catalyzes the phosphorylation of creatine, generating phosphocreatine (PCr) in the forward reaction, and regenerating ATP in the reverse reaction. Creatine kinase activity is inhibited by the creatine analog cyclocreatine (cCr). Loss- and gain-of-function genetic approaches were used in combination with cCr therapy to define the contribution of CKB expression or creatine kinase activity to cell proliferation, migration, invasion, and metastasis in ER-negative breast cancers. CKB was necessary for cell invasion in vitro and strongly promoted tumor growth and lung metastasis in vivo. Similarly, cyclocreatine therapy repressed cell migration, cell invasion, the formation of invadopodia and lung metastasis. Moreover, in common TNBC cell line models, the addition of cCr to conventional cytotoxic chemotherapy agents was either additive or synergistic to repress tumor cell growth.

RNA-binding protein IGF2BP2 suppresses metastasis of clear cell renal cell carcinoma by enhancing CKB mRNA stability and expression

“…The CKB gene is located on chromosome 14q32.33 and consists of seven exons [30] . CKB has been reported to exhibit abnormal expression in malignant tumors like prostatic cancer and breast cancer and play a pivotal role in tumorigenesis [ 31 , 32 ]. However, it's function has not been reported in ccRCC.…”

“…Subsequently, a series of experiments confirmed that IGF2BP2 bound to CKB mRNA to enhance its stability, and then promoted the expression of CKB. Several studies have reported significant differences in CKB expression in malignancies such as prostate cancer and breast cancer, emphasizing its crucial role in tumor progression [ 31 , 32 ]. Nevertheless, the biological function and mechanism in ccRCC remain unclear.…”

Acidic ascites inhibits ovarian cancer cell proliferation and correlates with the metabolomic, lipidomic and inflammatory phenotype of human patients

“…Finally, the negative correlation with creatine phosphate could also implicate that OC cells obtained their ATP mostly via fatty acid oxidation once they metastasized in the omentum. Overexpression of creatine kinase B (CKB) takes place in breast, colorectal, and OCs in response to acute hypoxia exposure [ 73 – 75 ] due to more ATP production demand for proliferation [ 52 , 76 , 77 ], which means hypoxic OC cells can elevate glucose consumption and lactate production, and decreased ROS production by CKB [ 78 ]. However, lactate production decreased or had a low negative correlation with pH, indicating less active glycolysis.…”