Clinical Significance of Carnitine in the Treatment of Cancer: From Traffic to the Regulation

Table 1

Important carnitine transporters, substrates, and related functions in cancers.

Carnitine transporter	Substrate	Cancer type	Mechanism of action	References
OCTN1/SLC22A4	Carnitine and acylcarnitine with low affinity, acetylcholine, ergothioneine, TEA	Acute myeloid leukemia (AML)	Transport of anticancer drugs such as daunorubicin and mitoxantrone	[26, 27]
OCTN2/SLC22A5	Carnitine, acetylcarnitine with the highest affinity, TEA, γ-butyrobetaine	High-grade serous epithelial ovarian cancer, breast cancer, lung adenocarcinoma, glioma, endometrial cancer, renal cancer, pancreatic cancer	Maintenance of carnitine homeostasis/β-oxidation, carcinogenesis and chemoresistance development, transport several anticancer drugs, such as imatinib	[28–31]
CT2/SLC22A16	Carnitine	Human epithelial ovarian cancer, gastric cancer, AML	Upregulation in gastric cancer, involving in drug delivery such as doxorubicin	[32–35]
ATB^0,+/SLC6A14	Carnitine with low affinity, all amino acids except aspartate and glutamate	Pancreatic cancer, colon cancer, estrogen receptor-positive breast cancer	Upregulated in solid tumors, used for drug delivery	[36–38]
CAC/SLC25A20	Carnitine, acylcarnitine	Bladder cancer prostate	Deregulated in tumor tissues of bladder cancer, overexpression in prostate cancer	[39, 40]
MCT9/SLC16A9	Carnitine	Breast cancer	Reduced survival	[41]