In a new study, researchers investigated the creatine shuttle pathway as a potential therapeutic target in colorectal cancer cells.
Since the 1992 Barcelona Olympics, creatine supplementation has increased in popularity and grown to widespread use amongst the mainstream public. Creatine is a naturally occurring compound, primarily stored in skeletal muscle and involved in energy production for high-intensity activities—enhancing performance and supporting muscle growth and strength. The process by which creatine is transported into the muscles and utilized for energy production is referred to as the creatine shuttle. While it is a useful mechanism for healthy muscles, the creatine shuttle has also been implicated in cancer.
“The creatine shuttle is highlighted in cancer as a source of energy for cancer cells that display aggressive proliferation, and aberrant creatine kinase (CK) levels are known to be associated with many malignancies and mitotic control .”
In a new study, researchers Mayu Kita, Rina Fujiwara-Tani, Shingo Kishi, Shiori Mori, Hitoshi Ohmori, Chie Nakashima, Kei Goto, Takamitsu Sasaki, Kiyomu Fujii, Isao Kawahara, Ujjal Kumar Bhawal, Yi Luo, and Hiroki Kuniyasu from Nara Medical University, Saveetha University and Nantong University hypothesized that the creatine shuttle is involved in energy metabolism and other adenosine triphosphate (ATP) supply in cancer cells. On May 19, 2023, their new research paper was published in Oncotarget’s Volume 14, entitled, “Role of creatine shuttle in colorectal cancer cells.”
“In the current study, the role of the creatine shuttle in CRC [colorectal cancer] was analyzed along with its potential as a therapeutic target.”
The Creatine Shuttle in Colorectal Cancer
Despite advancements in treatment options for colorectal cancer (CRC), incidence and mortality rates remain high. The metabolism of CRC cells is distinctly different from that of normal cells, and understanding these metabolic alterations is crucial for devising new targeted therapies. The creatine shuttle system plays a pivotal role in cellular energy metabolism, particularly in high-energy demanding tissues such as muscle and brain. However, its involvement in CRC cells has remained largely unexplored until now.
Creatine kinase, also known as CK or creatine phosphokinase, is an enzyme that catalyzes the transfer of a phosphate group from creatine phosphate to adenosine diphosphate (ADP), thereby regenerating adenosine triphosphate (ATP), which is the primary energy source for cells. CK exists in different forms or isoenzymes. In this study, the researchers investigated the expression and role of creatine kinase B (CKB) and mitochondrial creatine kinase (MTCK) in CRC tissues. They also explored the inhibitory effect of dinitrofluorobenzene (DNFB) on CKB and MTCK activity and its impact on CRC cell growth, stemness, mitochondrial function, energy metabolism, and cancer metastasis.
Inhibition of the Creatine Shuttle
The team used tissue arrays to examine CKB and MTCK expression in CRC tissues. Both proteins were highly expressed in high-grade tumors and cases with distant metastasis. Liver metastases showed higher expression compared to primary tumors, suggesting a role in CRC progression and metastasis.
DNFB, an inhibitor of CK activity, reduced CK activity and inhibited cell growth in CT26 and HT29 CRC cell lines. HT29 cells, with higher CKB and MTCK levels, were less sensitive to DNFB than CT26 cells. DNFB treatment decreased cell number, stem cell marker expression and impaired sphere formation in CT26 and HT29 cells. Knockdown of CKB or MTCK showed similar effects, indicating specificity to CK inhibition. DNFB also inhibited mitochondrial function and energy metabolism, decreasing mitochondrial membrane potential, increasing ROS production, and reducing OCR and ATP production in both cell lines.
In a mouse model of peritoneal dissemination, pretreatment with DNFB reduced tumor growth. Excised tumors from DNFB-treated mice showed decreased proliferation and stem cell marker expression, as well as reduced phosphorylation levels of tumor-promoting signaling molecules (EGFR, AKT, and ERK1/2).
Summary & Conclusion
“In this study, we showed that inhibition of the creatine shuttle by blocking CKB and MTCK activity suppressed the growth, stemness, and metastasis of cancer. It was suggested that the cause of this is related to inhibition of both mitochondrial energy metabolism and the phosphorylation signaling system.”
This research study provides valuable insights into the role of CKB and MTCK in CRC and highlights the therapeutic potential of inhibiting the creatine shuttle in CRC treatment. Inhibition of CKB and MTCK activity by DNFB impaired CRC cell growth, stemness, mitochondrial function, energy metabolism, and cancer metastasis. These findings suggest that targeting the creatine shuttle pathway may represent a promising therapeutic strategy for CRC patients. Further studies are warranted to validate these findings and explore the potential of targeting the creatine shuttle in clinical settings.
“Our data suggest that the antitumor effect of creatine shuttle inhibition can be attributed to the inhibition of mitochondrial energy production as well as the inhibition of multiple phosphorylation signals through inhibition of the ATP supply. Therefore, it is necessary to develop a new CK inhibitor to induce these two effects in vivo.”
Click here to read the full research paper in Oncotarget.
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