Cancer cells require several vital nutrients to reach their changing metabolic needs as they progress through stages of development compared to normal cells. Our findings depict that the root extract of
X. Strumarium has favorable anticancer activity in the epithelial ovarian cancer SK-OV-3 cell line. Like many other cancer types, epithelial ovarian cancer reprograms its metabolism during progression, converting from oxidative phosphorylation to glycolysis, a phenomenon recognized as the Warburg effect (
17). Alterations in several metabolic pathways, such as glycolysis, the tricarboxylic acid cycle, amino-acid metabolism, and lipid metabolism, were seen in the sera of epithelial ovarian cancer patients. These metabolic pathways are bonded, so their disruption leads to the initiation and progression of cancer (
18).
In this investigation, various metabolites altered after the cells were treated with root extract of X. Strumarium. Plotting these altered metabolites showed that Aminoacyl-tRNA synthesis, glycerolipid metabolism, fatty acid biosynthesis, and Biotin metabolism were the most affected metabolic pathways in cell growth inhibition.
The absorption of amino acids in cancer cells is faster than in healthy cells. It has been declared that balanced amino acid nutrients support the proliferation of cancer cells, whereas unbalanced amino acid nutrients suppress tumor cell proliferation (
19). It was reported that the reduction of essential amino acids leads to a disturbance in the metabolism of cancer cells and prevents the growth of tumors by inhibiting protein synthases (
20). The attachment of amino acids to specific tRNAs in protein synthesis is catalyzed by aminoacyl tRNA synthases, which play an essential role in the survival of cancer cells. Aminoacyl tRNA is the first protein biosynthesis product (
21). It was exposed that the destruction of leucyl tRNA synthases in lung cancer cells reduced the ability of cell migration and colony formation (
22). It has also been reported that increased expression of leucyl tRNA synthases was found in cancer cells, which seems to be recognized as a potential metabolic target (
23). Leucyl tRNA synthase is associated with the AIMP1 protein and other multi-functional proteins. In genotoxicity, these proteins stimulate the P53 activity, then adjust the P21 expression. P21 protein is an essential intermediate through which P53 promotes cell cycle inhibition (
24). It has been stated that serum tryptophanyl levels are related to colon cancer cells’ survival (
25). For glioblastoma multiforme tumors, it has been shown that the expression of several ARS genes, including CysRS, ASnRs, PhenRS, GlnRS, and ValRS, leads to more growth of cancer cells (
26). Also, it was proposed that increased expression of the ThrRS gene is directly related to the risk of ovarian, breast, and lung cancers (
27). In animal models, it was found that high levels of MetRS can be a marker for an increased risk of death due to lung cancer (
28). It was also reported that anti-ThRS could inhibit the growth of Jurkat and CEM cancer cell lines compared to control cells (
26). In this research, the metabolites of L-glutamine, L-alanine, L-tyrosine, L-proline, and Tetrahydrofolic acid altered the aminoacyl tRNA biosynthesis pathway. A comparison of our results with previous findings indicated that the root extract of
X. strumarium could disrupt the activity of tRNA synthase enzymes, thus, restricting the formation of the aminoacyl tRNAs, which inhibits the growth of SK-OV-3 ovarian cancer cells. Leucyl tRNA synthase and glutamyl tRNA synthase have more potential for metabolic anticancer targets than other enzymes.
Tetrahydrofolic acid, one of the metabolites altered in this pathway, is made by dihydrofolate reductase from folic acid, an inactive biochemical substance. Tetrahydrofolic acid enters the cells, used in red blood cell production, purine nucleic acid synthesis, thymidylate synthase metabolism, and amino acid metabolism (
29). Therefore, it seems that
X. strumarium root extract has inhibited the growth of the SK-OV-3 ovarian cancer cells, maybe by changing the tetrahydrofolic acid cofactor, the active form of folic acid, and also by disrupting the metabolism of amino acids.
Alterations in the normal metabolism of lipids, especially serum triglycerides, have been detected in patients with breast and ovarian cancer, which indicates a positive correlation between the level of triglycerides and the risk of progression of these cancers (
30). A positive relationship was reported between serum triglycerides and esophageal, colorectal, lung, renal, and thyroid cancer (
31). A partial connection was discovered between serum triglyceride levels and thyroid cancer in men and endometrial, cervical, and bladder cancer in women (
32). Also, a direct correlation was found between serum triglyceride levels and gynecological cancers (
33). In this research, Glycerol 3-phosphate, glycerol, and propylene glycol metabolites have changed in the glycerolipid pathway. According to the KEGG database, altered propylene glycol metabolite can motivate alcohol dehydrogenase enzyme, reducing propylene glycol and inhibiting the SK-OV-3 ovarian cancer cell line. Also, altered glycerol and glycerol 3-phosphate metabolites can cause disorders in fatty acid metabolism and the glycolysis cycle. Hence, it seems that
X. strumarium root extract was able to inhibit the growth of SK-OV-3 ovarian cancer cells, probably by reducing their energy.
Variations in lipid metabolism were discovered in patients with ovarian and recurrent cancer (
34). Fatty acid (FA) synthesis is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthase (FASN). In cancer cells, most FAs are synthesized by FASN for essential changes. Therefore, FASN has been considered a marker for diagnosis, prognosis, and a therapeutic target in cancer (
35). Palmitic acid promotes cell proliferation because of amplified expression of FASN in ovarian cancer cells, and suppression of this enzyme causes apoptosis and cancer cell death (
36). It was reported that increased FASN gene expression occurs in many tumors such as breast, prostate, colon, and ovary due to the non-reaction of tumors to regulatory messages and their greater affinity towards the lipogenesis pathway (
37). It has been revealed that stearic acid has a negative role in DNA damage that stimulates cell alteration and tumor genesis (
36). It has also been detected that decreased levels of stearic acid and oleic acid in serum-initiated malignancy in cells (
38).
It was reported that an increase in oleic acid and a decrease in stearic acid was shown in several cancer types such as breast, liver, lung, pancreas, colon, and prostate (
39). It has also been exposed that oleic acid has inhibited the activity of FASN, and the malonyl CoA has accumulated, suppressing HER2 oncogene expression (
40,
41).
This research alters oleic acid, capric acid, and stearic acid metabolites in fatty acid biosynthesis. Therefore, oleic and stearic acid can be potential therapeutic targets in ovarian cancer. A comparison of our results with previous findings revealed that X. Strumarium root extract could probably prevent the growth of SK-OV-3 cancer cells by inhibiting FASN activity.
Biotin is an essential cofactor for carboxylases made from pimelic acid, coenzyme A, ATP, and mg2+. It has been demonstrated that altered pimelic acid inhibits biotin production. Biotin disturbs the activity of the pyruvate carboxylase enzyme. It disrupts the gluconeogenesis pathway in cancer cells, leading to the inability of cancer cells to produce glucose and a decrease in cellular energy (
42). It was also reported that altered pimelic acid had inhibited biotin synthesis, and the acetyl-CoA carboxylase enzyme has been disrupted, preventing malonyl CoA production, a substrate for fatty acid synthesis. Finally, the fatty acid biosynthesis pathway has been disturbed, and cancer cells’ energy has been reduced (
43). In this research, pimelic acid metabolite has changed in the biotin metabolism pathway, so pimelic acid can be a potential therapeutic target in ovarian cancer. A comparison of our findings with previous results represented that
X. strumarium root extract could probably inhibit the growth of SK-OV-3 ovarian cancer cells by disrupting the biotin metabolism pathway, disrupting fatty acid synthesis, and reducing cellular energy.
5.1. Conclusions
In the present investigation, the ethanolic root extract of X. Strumarium reveals antitumor activity against SK-OV-3 ovarian cancer cells. Lipid metabolism was the most affected metabolic pathway involved in cell growth inhibition and could be a potential medicine target in ovarian cancer treatment. However, further studies are required to validate these findings along with the various potential fractions of the root extract of this plant, in addition to the SK-OV-3 cell’s transcriptome and genomic data.