Assessment of an antitumor effect of 2-(6,8-dimethyl-5-nitro-4-chloroquinoline-2-yl)-5,6,7-trichloro-1,3-tropolone in A-549 tumor cell subcutaneous xenografts

Abstract

Rationale: Chemotherapy is one of the lung cancer treatment methods. The search for new substances with antitumor effect against malignant lung neoplasms is relevant because of low efficacy and side effects of cytotoxic agents. A promising substance class with various biological activities, including antitumor, includes alkaloids of the tropolone family, such as heptamerous non-benzoid aromatic compounds. 2-(6,8-dimethyl-5-nitro-4-chloroquinoline-2-yl)- 5,6,7-trichloro-1,3-tropolone has been synthesized in Institute of Physical and Organic Chemistry; it is a  new compound belonging to 2-quinoline-2-yl derivatives of 1,3-tropolone.Aim: To assess the antitumor effect of 2-(6,8-dimethyl-5-nitro-4-chloroquinoline-2-yl)- 5,6,7-trichloro-1,3-tropolone on subcutaneous xenografts of A-549 lung tumor cells in immunodeficient Balb/c Nude mice.Materials and methods: The study included 50  immunodeficient Balb/c Nude mice divided into 4  experimental groups depending on the dosage of the study substance (0.0055, 0.055, 0.55, and 2.75  mg/g); group 5  was the control group. A-549  cells of lung cancer were used as a xenograft. The antitumor effect of tropolone was evaluated by the inhibition of tumor growth and the index of tumor growth. The experiment lasted for 36 days starting from the first administration of the substances.Results: The mean tumor volumes on day 36  of the experiment in the control group and four experimental groups were 2729.5; 2150.8; 1746.4; 952.3  and 678.9  mm3 , respectively. The indices of tumor growth in groups  1, 2, 3 and 4 were significantly lower than in group 5 (control) starting from days 24, 21, 21 and 15, respectively, and till the end of the experiment. Maximal differences between groups 4 and 5 were observed at days 33 and 36 (by  3.7, p=0.01 and 4.1, p=0.003  times, respectively).Discussion: The anti-tumor effect of 2-(6,8-dimethyl-5-nitro-4-chloroquinoline-2-yl)- 5,6,7-trichloro-1,3-tropolone demonstrated in the study could be related to various mechanisms. For example, numerous studies have shown that its related compound hinokitiol exerts a cytotoxic effect associated with cessation of the cell cycle, apoptosis induction, DNA damage, and autophagic death of tumor cells.Conclusion: The study demonstrated significant differences in xenograft volumes in all experimental groups, compared to the control group. In mice, 2.75  mg/g bodyweight was the most effective dosage of the studied compound leading to a slow decrease in tumor growth rates and a  decrease in the volumes of subcutaneous xenografts.