*2.4. Tanshinone Maintains Gene Stability of PCa Cells*

Tanshinone also regulates the expression of epigenetic-modification-related genes in PCa cells. Among 84 epigenetic-modification-related genes in PCa cells treated with Tanshinone (mainly TsI), the expression of 32 genes was down-regulated [30], including AuroraA kinase, DNA methyltransferase, histone acetyltransferase, histone deacetylase, Lysine (K)-specific demethylase, and protein arginine methyltransferase. The PCa cells treated with CYT and TsIIA only had the expression of AuroraA kinase inhibited. However, previous studies have shown that epigenetic disorders such as histone modification and DNA methylation contribute to the initiation and progression of PCa. AuroraA kinase is a key mitotic regulator required to maintain chromosome stability [73], and its overexpression often indicates a higher degree of malignancy in tumors. In addition, Tanshinone has been reported to be significantly associated with the down-regulation of astrocyte elevating gene 1 (AEG-1) in PCa cells [31], which is involved in the regulation of multiple signaling pathways in cancer cells, including PI3K/Akt, NF-κB, Wnt/-catenin, and MAPK. They synergistically promote the oncogenic and metastatic potential of transformed cells [74]. In addition, Tanshinone can reduce the transcription and translation of topoisomerase 2A in PCa cells [52], which is critical for genomic stability and replication. Interestingly, Tanshinone has been reported to regulate the activity and elongation of the RNA-binding protein HuR and telomerase. This coordinates mRNA stabilization and translation [75–78], which is critical for inflammation and tumor progression.

In fact, the antioxidant capacity of Tanshinone also plays a significant role in maintaining the genetic stability of prostate cancer cells. Although this has not been confirmed, studies have shown that oxidative stress can often damage DNA molecules, leading to the occurrence of tumors [79]. However, the specific antioxidant activity of Tanshinone is that it can effectively inhibit the interaction between DNA and intracellular lipid peroxidation products, thereby stabilizing DNA molecules [80]. However, the current research does not pay attention to the influence of Tanshinone on the factors and pathways related to oxidative stress in prostate cancer cells. Secondly, the special skeleton structure of Tanshinone also has an effect on the stability of DNA. It is reported that the Tanshinone D ring can bind to the small grooves in DNA molecules, thereby stabilizing DNA molecules [23,25]. In addition, the regulatory effect of Tanshinone on microRNAs in prostate cancer cells seems to be involved in this process. After all, microRNAs are closely related to gene expression and synthesis, and mutations of microRNAs often lead to cancer [81,82]. Unfortunately, although Tanshinone has been proven to be able to regulate microRNAs in other cancer cells [27,83], the current study has not confirmed the regulatory effect of Tanshinone on microRNAs in prostate cancer cells. Based on the fact that microRNA not only plays a key role in the process of gene expression and synthesis but also has significant significance in maintaining the malignant behavior of cancer cells, future research should also pay attention to the regulatory effect of Tanshinone on microRNA in prostate cancer cells. In conclusion, the current research is limited. Although laboratory data have confirmed that

Tanshinone has the ability to stabilize the genetic stability of prostate cancer cells, there is no exact evidence and the corresponding mechanism is not clear.

#### *2.5. Tanshinone Reverses Multidrug Resistance in PCa*

Tanshinone also has a regulatory effect on multidrug resistance (MDR) of tumor cells, and MDR is the main factor for clinical chemotherapy failure. Although chemotherapy is not recommended as a first-line treatment for PCa in the early stages of the disease, it is often recommended as a first-line treatment for PCa in the advanced stages [84,85]. Existing literature shows that Tanshinone can adjust the genes associated with MDR (P glycoprotein, topoisomerase, lung resistance protein expression) to reverse the drug resistance of tumor cells to chemotherapy drugs [86]. Although this has not been confirmed in PCa, it is interesting to note that after Tanshinone pretreatment, the toxic effects of cisplatin and azithromycin on PCa increased [36,60]. In addition, tumor stem cells are also considered to be one of the key factors in the occurrence of MDR [87]. It is noteworthy that Tanshinone has also shown a regulatory effect on tumor-initiating cells in PCa. In an experiment, YingZhang et al. found that Tanshinone can regulate the expression of prostatic cancer cell globogenesis and stem cell genes (Nanog, OCT4, SOX2, -catenin, CXCR4) and simultaneously change the cell proliferation, cell cycle state, migration, and colony formation of prostate tumor-initiating cells (CD44 + CD24-population) [57]. This could be because Tanshinone significantly reduced Bmi1 gene expression and protein levels (key regulators of stem cell self-renewal and malignant transformation) [88].

Tanshinone can prevent the occurrence of MDR in prostate cancer cells by downregulating the genes related to the occurrence of MDR and inhibiting the tumor-initiating cells closely related to the occurrence of MDR. It is worth noting that Tanshinone can also greatly improve the adverse reactions caused by radiotherapy and chemotherapy [89]. Research shows that Tanshinone can significantly improve the organ nerve loss caused by radiotherapy and chemotherapy [89,90]. Therefore, based on the current research, we believe that Tanshinone combined with radiotherapy and chemotherapy in the treatment of drug-resistant prostate cancer will become a possibility. However, the current research is limited, and the specific mechanism of Tanshinone enhancing the toxic reaction of chemotherapy drugs to prostate cancer is still unclear, so further research is needed.

#### *2.6. Tanshinone Changes the Metabolic Process of PCa*

Tanshinone has also been reported to regulate the metabolic process of PCa. Existing publications show that the expression of some genes related to steroid and cholesterol biosynthesis in PCa cells treated with Tanshinone (mainly Tanshinone IIA) is significantly reduced [91], including methylsterol monooxygenase 1 (MSMO1/SC4MOL), squalene monooxygenase (SQLE), ATP-binding box subfamily G member 1 (ABCG1) and preprotein invertase subtilin kexin9 (PCSK9s). Although this has not been proven to be associated with tanshoneinhibition of PCa, it is worth mentioning that Tanshinontong changes the way tumor cell metabolism works, including down-regulating the enzymes involved in glucose uptake and metabolism in cancer cells (especially those related to glycolysis), affecting the energy metabolism of tumor cells, and then inducing apoptosis of cancer cells [92,93].

It is reported that in the process of progression, tumors often change their metabolism to quickly obtain energy or synthesize substances they need [94]. This process is critical for prostate cancer. Previous studies have shown that advanced prostate cancer may be more dependent on lipid metabolism. The expression of genes related to lipid synthesis in advanced prostate cancer cells is significantly higher than that in early prostate cancer cells [95,96]. Prostate cancer increases the synthesis of its own lipids in this way, thereby providing more abundant raw materials for androgen synthesis so as to tolerate the low level of androgen brought on by castration treatment [96,97]. Therefore, regulating the metabolism of prostate cancer has significant significance for the treatment of prostate cancer. As evidenced based on appeal, the metabolic rearrangement of Tanshinone on prostate cancer cells should also be paid attention to in future research. The molecular mechanism involved should also be further explored.
