Anti-angiogenic treatment is an effective and targeted therapy strategy that can be used to control and kill tumors (1). Although chemotherapeutics can kill tumor cells, the remaining tumor cells can still survive and continue to grow due to the support of peripheral blood vessels. Meanwhile, abnormal tumor blood vessels reduce the delivery of drugs into tumor tissues, which ultimately leads to limited efficacy of anti-cell proliferation therapy. Therefore, the treatment for cancer should not only be directed against tumor cells, but also against the tumor microenvironment, in particularly tumor angiogenesis (2).

Vascular endothelial growth factor (VEGF) is the master effector of the angiogenic response in cancers (3). Anti-angiogenic drugs can be used to specifically bind to VEGF to prevent it from interacting with receptors, which play a critical role in tumor blood vessels. Further, this limits exposure to oxygen and other nutrients required for tumor cell growth, thereby weakening the ability of tumor growth and metastasis. Anti-angiogenic agents targeting the VEGF and HIF-α pathways include monoclonal antibodies to VEGF (4), such as bevacizumab and resumumab, small-molecule tyrosine kinase inhibitors (TKIs), such as anlotinib, sorafenib, and sunitinib, and VEGF receptor (VEGFR)2 inhibitors, such as regorafenib and ramucirumab (5). These compounds can lead to a reduction in the tumor blood supply and growth of the tumor blood vessels. Unfortunately, cardiovascular toxicity is a potential limitation associated with the long-term use of anti-angiogenic agents in cancer and requires further study to assess the value of anti-angiogenic treatment.

Aspartate aminotransferase (AST) is a pyridoxal-5′-phosphate-dependent enzyme that is widely distributed in heart, liver, skeletal muscle, kidney and brain. It plays a key role in the metabolism of amino acids, synthesis of purine/pyrimidine bases, urea and protein synthesis, and gluconeogenesis (6). Lactic dehydrogenase (LDH) is a type of enzyme, which plays an important role in making body's energy. It can be found in almost all the body's tissues, including those in the blood, heart, kidneys, brain, and lungs. LDH is released from damaged tissues, and can serve as a biomarker for damaged heart tissue. Creatine kinase (CK) is a guanidino-kinase that catalyzes the reversible phosphorylation of creatine to phosphocreatine, and is primarily distributed in bone and myocardium. The plasma activity of creatine kinase isoenzyme (CK-MB), one of the isoenzymes of CK, is generally used to evaluate acute coronary syndrome. The detection of serum CK isozymes, especially serum CK-MB, is helpful for judging the degree of myocardial injury. Comprehensively, monitoring serum AST, LDH, CK and CK-MB activities for cardiac biomarkers can be valuable for assessing patient status (7, 8).

Unfortunately, few studies have focused on the measuring changes in serum AST, LDH, CK and CK-MB activities before and after anti-angiogenic treatment for cancer. In this study, we conducted a retrospective investigation focused on measuring the changes in serum AST, LDH, CK and CK-MB in serum on cancer patients receiving anti- angiogenic targeted therapy. The results suggested that in serum AST, LDH, CK and CK-MB activities of patients who had used anti-angiogenic drugs were likely to have elevated.

This retrospective study revealed the blood biomarkers, such as AST, LDH and CK were markedly increased with use of anti-angiogenic drugs, indicating that use of anti-angiogenic drugs may be related to an increased risk of myocardial damage. Moreover, serum CK and CK-MB activities have been affected by history of prior heart disease, cardiovascular drugs, and smoking. The determination of myocardial enzymes mainly includes AST, LDH, CK and CK-MB. When the cardiomyocytes have inflammation (myocarditis) or necrosis (myocardial infarction) due to various reasons, the enzymes contained in the cardiomyocytes can enter the blood, and the activity (content) of these enzymes in the blood increases. Elevation of these serum markers in this study did not exceed the normal upper limit, but it may indicate a tendency for long-term use to accumulate toxicity.

AST is one of the most important aminotransferases in the body. It is mainly found in tissue cells such as myocardium, liver, skeletal muscle, kidney, pancreas, spleen, lung, red blood cells, as well as in normal human plasma, bile, cerebrospinal fluid, and saliva. Medium, but it cannot be detected in urine without kidney damage. The content of AST in the myocardium is the most abundant, so it has certain significance for the diagnosis of myocardial infarction. When acute myocardial infarction (AMI) occurs, the serum AST activity generally rises to 4–5 times the upper limit of the reference value. If it reaches 10–15 times the upper limit of the reference value, it is often fatal infarction occurred. However, the rise of AST is later than CK in AMI, and recovers earlier than LDH, diagnostic value of AST for AMI is becoming less and less. Nevertheless, AST is an indispensable evaluation index in the clinical research of oncology drug evaluation. The study determined the safety and effectiveness of anti-angiogenic therapy with sorafenib and bevacizumab in patients with advanced HCC and results found that dose-limiting toxicities included hypertension, AST increase, creatinine increase, etc. (9). Patients receive intravenous ramucirumab (8 mg/kg) every 2 weeks were observed in a phase 3 clinical trial. Hypertension (34 [12%] of 277 patients treated with ramucirumab), increased AST concentration (15 [5%]), thrombocytopenia (13 [5%]), etc. were occurred with grade 3 or greater adverse events (10). LDH is an extremely important enzyme that regulates the conversion of pyruvate to lactic acid in anaerobic glycolysis and play an important role in cancer metabolism (11). Meanwhile, LDH is a useful marker for predicting the efficacy of bevacizumab-containing chemotherapy in patients with metastatic colorectal cancer (12). It is widely present in the cytoplasm and mitochondria of tissue cells such as liver, heart, skeletal muscle, lung, spleen, brain, red blood cells, platelets, etc. LDH is a tetramer composed of two different subunits (LDHA and LDHB), forming 5 isoenzymes with M-type and H-type subunits: H4(LD1), MH3(LD2), M2H(LD3), M3H(LD4), M4(LD5). Different tissues have their characteristic isoenzymes. The ratios of LD isoenzymes in the heart, kidney and red blood cells are similar, with LD1 and LD2 dominating. When the myocardium is damaged, the myocardial cell membrane ruptures, and the mitochondria and cytoplasmic substances leak out into the intercellular fluid and periphral blood. In response to the hypoxic characteristic of the tumor microenvironment, cancer cells generate a large amount of lactate via the metabolism of glucose and glutamine (13, 14). High levels of LDHA expression serves as a prognostic indicator in patients with different type of cancers (15). LDH increased production of reactive oxygen species and regulate cell apoptosis and autophagy (16). Thus, the role of LDH in tumor biology is more complex and may as a potential target in the treatment of cancer. Although in this study, the elevation of AST and LDH in patients did not exceed the normal upper limit, there was a significant increase in serum AST and LDH activities, compared with the matched healthy control.

But it is regrettable that the serum CK and CK-MB activities of matched healthy control were not found. All healthy control were from a medical examination at our hospital, serum CK and CK-MB activities are not included in the physical examination at present. Interestingly, serum CK and CK-MB activities have been affected by history of prior heart disease, cardiovascular drugs, and smoking.

CK mainly exists in skeletal muscle and cardiac muscle, and brain tissue. CK is an important energy regulating enzyme in the myocardium. Under the energy provided by ATP, it catalyzes the reversible phosphorylation of ATP and creatine to ADP and phosphocreatine in cellular energy metabolism, which can be transported to the cytoplasm and stored. Serum CK can be increased in various types of progressive muscle atrophy. CK begins to increase 2–4 h after AMI and can reach 10–12 times the upper limit of normal. It has higher specificity than AST and LDH for diagnosing myocardial infarction, but the increase of this enzyme lasts for a short time, and it returns to normal after 2–4 days. There are three isoenzyme formations for CK: CK-MB (mostly in the heart), CK-MM (mostly in the muscle), or CK-BB (mostly in the brain) (17). CK-MB activity has been recognized as a specific and sensitive biomarker of clinical and subclinical myocardial injury (8, 18). CK-MB activities are significantly positively correlated with the extent of myocardial injury, so serum CK-MB can be used as a biomarker for AMI (19). The presence of CK-MB in patients with cancers may cause confusion with AMI. Serial determinations of both CK and LDH are of great help in differential diagnosis 3512170. In addition, a previous study demonstrated that an elevated serum CK-MB in cancer patients may be associated with cardiac insufficiency, severe illness status, and have high mortality (20). Even a slight increase in CK-MB indicated the possibility of myocardial infarction (21). There has been no retrospective report focusing on CK, CK-MB and anti-angiogenic therapy. In the present study, both CK and CK-MB levels were significant elevated after use anti-angiogenic drug. Myocardial ischaemia might be the reason for the slight increase in CK and CK-MB. Furthermore, Some studies have demonstrated that CK-MB-to-total-CK ratio could be clinically utilized as a primary screening tool for cancer (22), which is an easily available indicator. In this study, we found that patients who had prior heart disease history had a higher serum CK-MB activities, while in patients who had cardiovascular drugs history had a lower serum CK and CK-MB activities on the contrary. The reason for the result is likely to be that people with previous cardiovascular disease have damage to heart muscle cells, while the drugs reduce the damage, which need to be further studied.

Our findings suggest that the serum AST, LDH and CK activities of patients who had used anti-angiogenic drugs were likely to have elevated. History of prior heart disease, cardiovascular drugs, and smoking should be considered in the anti-angiogenic treatment. AST, LDH, CK and CK-MB are indicators of myocardial muscle injury, such as myocarditis or myocardial infarction. Use of anti-angiogenic drugs should not be assumed to be completely safe and without any cardiovascular risks. In addition, attention should also be paid to long-term use to accumulate toxicity. Apparently, the number of cases in patients should be expanded and more detailed research should be done in the future.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

This was an observational, retrospective study that obtained informed consent from all subjects, and this research was approved by the Ethics Committee of Guang'anmen Hospital, China Academy of Chinese Medical Sciences with code number 2020-073-KT. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.

QZ and YZ: conception and design and manuscript writing. YZ and WH: administrative support and manuscript edition. QZ and HW: data extraction and data analysis. All authors contributed to the article and approved the submitted version.

This work was supported by the Fundamental Research Funds for the Central public welfare research institutes (2020YJSZX-3), National Natural Science Foundation of China (No. 82104656) and Beijing Municipal Natural Science Foundation (7214294).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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