Avaliação dos efeitos de p-cimeno em câncer: revisão de escopo e estudo In vitro

Abstract

Conventional oncological therapies tend to mutilate patients and generate pharmacological resistance and adverse effects. The use of natural compounds stands out as an alternative in this therapy, as it minimizes the deleterious effects and enhances the action of chemotherapeutics, acting as an adjuvant. P-cymene (pC), a monoterpene present in several plants, has already been evaluated in preclinical cancer studies, showing preventive and therapeutic effects. However, these findings need to be better mapped and analyzed in order to elucidate the best strategies for using this compound in cancer therapy. This thesis aimed to review and map the published findings on the actions of pC in cancer, as well as to evaluate the in vitro activity of this compound in two oral cancer cell lines. For this, a scoping review was performed using PRISMA-ScR as a guide and using the bibliographic databases Embase, Scopus, Pubmed and Web of Science for the selection of studies. The laboratory study was based on cell cultures of the following cell lines: UM-HACC-2A (salivary adenoid cystic carcinoma), in which cell viability assays (Live/Dead assay method) were performed to obtain the IC50 of pC, immunofluorescence of NFκB and Ki-67, cell migration and analysis of the nuclear area; SCC-4 (oral squamous cell carcinoma), in which cell viability assays (MTT method), gene expression of Caspases 3 and 9, Bcl-2 and Akt, immunocytochemistry of PI3K, Ki-67 and Akt proteins, as well as cell migration were performed; and HaCat (normal keratinocytes), as control. The Shapiro-Wilk test, t-test, Mann-Whitney test and nonlinear regression were the statistical methods applied, with a significance level of 5% (p<0.05) adopted for all analyses. The results of the scoping review revealed that 93.7% of the included in vitro studies showed pC IC50 values considered to be of low cytotoxic potential by the National Cancer Institute (NCI), with a mean value of 178.43 μg/ml, being tested in colorectal, breast, lung, liver, cervical, skin, fibrosarcoma and melanoma cancers and acting mainly through non-cytotoxic mechanisms, such as alteration of cell signaling pathways (inhibition of ERK1/2 and p38 MAPK and activation of TIMP-1), modulation of the tumor microenvironment (reduction of SOD, increase of IL-6 and reduction of IL-1) and inhibition of invasion (reduction of MMP-9), and secondarily through cytotoxic mechanisms, such as DNA damage (increase of 8-OHdG) and plasma membrane (increase of malondialdehyde), and increase of Caspase-3 activity. Animal studies have shown significant results in reducing the incidence of tumors in colorectal cancer and tumor size in colorectal cancer and melanoma. The results of the in vitro study demonstrated low cytotoxicity of pC in UM-HACC-2A (IC50=664.7 μg/ml), in SCC-4 (IC50=573.6μg/ml) and in normal keratinocytes (IC50=694,6 μg/ml), with a selectivity index (SI) of 1.12. In the UM-HACC-2A cell line, significant inhibition of the expression of NFκB (p=0.026) and Ki-67 (p=0.005) proteins was observed, as well as a reduction in nuclear area (p<0.0001), but there was no statistically significant difference in the migration of UM-HACC-2A cells. In SSC-4 cells, there was inhibition of cell migration (p=0.0005), reduction in the expression of PI3K, Ki-67 and Akt proteins (p=0.0286); however, no significant changes were observed in the gene expression of Caspase 3 and 9, Bcl-2 and Akt. It is concluded that, although pC presents low direct cytotoxicity against tumor cells, its effects on cell signaling pathways, tumor microenvironment, cell invasion and migration processes, as well as chemoprevention in animal models, suggest its use as an adjuvant agent in oncological therapy, acting as a modulator of tumor progression and potentially increasing the efficacy of conventional cytotoxic therapies. Continued studies, with emphasis on in vivo models and proteomic analyses, are essential to deepen the knowledge about its mechanisms of action and therapeutic potential.