Potential of Thai Medicinal Plants as an Alternative Cancer Treatment

Abstract

Cancer is the most common health problem worldwide. The incidence of cancer has been increasing every year and cancer is a major cause of death in the world including Thailand. The statistic information from the Ministry of Public Health, Thailand, indicates that from 2015 to 2019, cancer is the most mortality rate in the Thai population. Classification of cancer types for mortality rates demonstrates that the most three mortality cancer types in the Thai population are liver cancer, lung cancer and breast cancer, respectively. Therefore, these three cancer types were selected for examining in this study. There are several strategies for cancer therapy including surgery, radiotherapy, chemotherapy, hormonal therapy, and target therapy. However, cancer treatments are limited by the aggressive and invasive cancer stage, these lead to more difficult therapy and a high chance of cancer therapeutic resistance. Moreover, the side effects of the therapy are the main problems for the quality of life of cancer patients. These bring the focus of some medical research to study herbal plant extracts for alternative cancer treatment. Also, the discovery and development of novel drugs for better efficiency, fewer side effects and drug resistance improvement are required. In this study, eighteen kinds of the medicinal plant from the Plant Genetic Conservation Project under the Royal initiative of Her Royal Highness Princess Maha Chakri Sirindhorn (RSPG) were extracted by using 50% ethanol as the solvent. Then, the extracts were examined the cytotoxicity against three types of cancer cell lines including A549 lung cancer cell, MDA-MB-231 breast cancer cell and HepG2 liver cancer cell by MTT assay. The results showed that only PZ reduced A549 cell viability until IC50 available to calculate. Both MG and PY trended to decrease the viability of cancer cell lines but not until getting IC50. So, the plants of MG, PY and PZ were selected to extract with another solvent. Ethyl acetate (EA) was used as another solvent, then these three EA extracts: EA-MG, EA-PY and EA-PZ, were determined the cytotoxicity against the three cancer cell lines. The results showed that all EA extracts decreased the A549 cell viability and IC50 could be calculated, so EA-MG, EA-PY, EA-PZ and PZ are the effective extracts for anti A549 lung cancer cell in this study. Moreover, EA-MG and EA-PY effectively reduced the viability of MDA-MB-231 cells with getting the IC50. For HepG2, even EAPY could reduce the cell viability but the results did not in a dose-dependent and the IC50 was higher than other cells’ effective extracts. So, HepG2 was excluded from further experiments. The four effective extracts in this study were examined for the phytoconstituents by GC-MS analysis and the identifiable compounds in EA-MG, EAPY,EA-PZ and PZ were reported. Lung cancer, which was inhibited viability by the most several types of herbal extracts in this study, was more investigated on the combination effect between the effective extracts and conventional chemotherapy drugs. The results demonstrated that three synergistic combinations of EA-MG with methotrexate, PZ with methotrexate, and PZ with etoposide. Additionally, the primary lung cells from lung cancer patients were examined as an ex vivo experiment. The cytotoxicity of the four effective extracts was measured against primary lung cancer and normal cells. The significantly different IC50 between cancer and normal primary cells was presented only treatment of PZ. Moreover, these four effective extracts were investigated the induction of apoptosis cell death. The effective extracts induced A549 cell apoptosis was examined by PI staining for cell morphology and annexin V/PI apoptosis assay. Also, mitochondrial dysfunction was induced by the effective extracts that were determined by the assessment of ∆Ψm loss and intracellular ROS production. The results of apoptosis induction were confirmed by upregulation of Noxa gene and protein levels. Therefore, these four effective extracts induced mitochondrial dysfunction and apoptosis cell death in A549 cells. The effective extracts of MDA-MB-231 breast cancer cell, EA-MG and EA-PY, were investigated for the mechanism of cancer cell death. Mode of cell death was determined by annexin V/PI assay and the results showed that EA-MG and EA-PY significantly increased the percentage of both early and late apoptotic cells. Then, the EAMGand EA-PY induced mitochondrial dysruption were determined and the results showed the reduction of ∆Ψm and generation of intracellular ROS. The intrinsic and extrinsic apoptosis pathways were identified by caspases activity. The EA-MG and EA-PY increased the activities of caspase 9 and 3 but not caspase 8, these suggested the extracts induced MDA-MB-231 cell death via the intrinsic apoptosis pathway. Also, the Bcl-2 family proteins have measured for the expression of Noxa and Bax (pro-apoptotic proteins), and Bcl-xL (anti-apoptotic protein) in both gene and protein levels. The results demonstrated that the extracts upregulated gene and protein levels of Noxa and Bax, whereas downregulated Bcl-xL. Moreover, cytochrome c which is the key component of the apoptosome that activates the caspase 9 and 3 cascades, was determined for their protein levels. The results showed that the extracts increased the cytochrome c protein level in cytosol whereas decreased it in the mitochondrial compartment. These suggested that EA-MG and EA-PY induced the intrinsic apoptosis pathway in MDA-MB231 cells via the activity of Bcl-2 family protein, mitochondrial disturbance,and caspase 9 and 3 cascades In conclusion, these four effective extracts from 3 different kinds of Thai medicinal plants possess the potential of alternative cancer treatment. Either B. ovata or C. oblongifolius have presented the efficiency of cancer therapy in both lung and breast cancer. Although, E. succirubrum was shown the efficiency of cancer treatment only in lung cancer, the ethanolic extract of E. succirubrum is the most effective results both on A549 lung cancer cell line and primary lung cancer cell. Therefore, further study and development of these three medicinal plants may be advantageous as an alternative cancer therapy in the future.