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Background: Orthotopic patient-derived xenografts (PDX) in immunodeficient mice are recognized as the most adequate neoplastic model due to their ability to maintain primary tumor properties after implantation. They can be used to study anti-neoplastic effects of pharmacological substances in vivo and to investigate characteristics and mechanisms of carcinogenesis. Results of preclinical studies of pharmacological substances obtained with PDX models are virtually no different from those of subsequent clinical trials. Aim: To develop an orthotopic PDX model of a highly differentiated human pancreatic neuroendocrine tumor (pNET) by implanting a fragment of the patient's tumor into the pancreas of immunodeficient mice. Materials and methods: A tumor fragment was obtained from a patient with a highly differentiated pNET G2 and liver metastasis. Fifteen (15) male immunodeficient Balb/c Nude mice with a mass of 22-24 grams were used to establish the orthotopic PDX model of human well-differentiated pNET. A fragment of primary pNET was orthotopically transplanted into the pancreas of 10 animals. A fragment of the metastatic lesion was transplanted into the liver of 5 animals. The animals were followed for up to 45 days. In vivo monitoring of the tumor growth was performed with a magnetic resonance imaging (MRI) system (ClinScan, Bruker BioSpin, Rheinstetten, Germany). At the end of the experiment, animals were euthanized and autopsies were performed, with routine histopathological examination and immunohistochemical study with antibodies to human chromogranin A, synaptophysin, and the marker of proliferative activity (Ki-67) of both original donor tumor and orthotopic pancreatic and liver xenografts. Results: Obvious changes in the mice condition were noticed at 30 days after surgery. They manifested as an increase in abdominal distension, swelling, and cyanosis in the projection of the pancreas. MRI showed a homogeneous neoplasm in the pancreas. At autopsy, the engraftment rate was 73% of all study animals, with yellow masses with even contours and a volume of about 100 cm3 present within the yellow-pink pancreatic tissues. The morphological assessment showed histological similarity between the original patient's tumor and patient-derived xenografts, which were identified as highly differentiated G2 pNETs. At immunohistochemical assessment, the patient's primary and metastatic tumor tissue specimens expressed anti-chromogranin A (full-blown cytoplasmic reaction) and anti-synaptophysin (mild cytoplasmic reaction) antibodies. Ki-67 was positive in 5.2% of the cells. An immunohistochemical study of the orthotopic tumor fragments and heterotopic tumor fragments showed moderate cytoplasmic staining with antibodies to chromogranin A and synaptophysin. The rate of Ki-67 in the orthotopic pNET model and metastatic model does not exceed 5% and 8%, respectively. Conclusion: Engraftment of tumor material after transplantation of human pancreatic cancer was observed in 73% of the cases, which should be considered a good first passage implantation result. The morphological studies confirmed that the orthotopic PDX was a well-differentiated pNET, histologically corresponding to the donor tumor. The model created in the experiment mirrors the histological characteristics of the donor tumor and can be used in preclinical studies of new treatments for well-differentiated pNETs, including those of antitumor activity of new pharmacological substances.

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.