Investigation of the apoptotic effects of some medicinal herbal aromatic oils on colorectal cancer cell lines and determination of potential target gene expressions

In recent years, the incidence and death rate of colorectal cancer has increased in develo ping countries. This makes colorectal cancer the third most common type of cancer in the world while keeping it the second most common cause of death among cancers. Although treatments such as surgery, chemotherapy or radiation therapy are useful to treat colorectal cancer patients, metastases or recurrences may still take place. Therefore, there is a need for alternative treatment methods that can give effective results in cancer pathogenesis studies. One of these alternative treatment modalities is known as essential oils with natural bioactive compounds/phytochemicals which are obtained from medicinal plants. It is reported that essential oils show various biological activities such as antimicrobial, antiviral and antifungal due to the many bioactive compounds they contain. In this thesis, it was aimed to investigate the apoptotic effects of clove and thyme essential oils on the colorectal cancer cell lines (HCT-116 and SW620). Since the pathogenesis of colorectal cancer is quite complex, the expression levels of genes that play a role in inflammation and apoptosis may affect this process. In this thesis study, the expression levels of some genes (COX-2, BCL-2, FAS, DR4 and DR5) that are effective in apoptosis and inflamma tion were examined. For this purpose, cell viability was determined by MTT test and gene expression levels were determined by qRT-PCR. According to the obtained data, both essential oils that applied showed dose-dependent cytotoxic activities. Clove essential oils showed more cytotoxicity than thyme essential oil. In addition, essential oils treat ment slightly decrease the expression levels of apoptosis-inhibiting gene BCL-2 and COX-2 genes in HCT-116 and SW620 cell lines, but this change was not statistically significant. On the other hand, it was revealed that thyme essential oil significantly inc reased the expression levels of the pro-apoptotic gene DR4 in both colorectal cancer cell lines, in addition, it was able to induce FAS expression in HCT-116. As a result, it was revealed that thyme essential oil, one of the essential oils used in the current study, has potential apoptotic effects on colorectal cancer compared to clove and may play a role in cancer treatment. However, it should be stated that further studies are required to identify the active compounds of clove and thyme essential oils and to analyze their efficacy.