Abstract 3130: Evaluation of TK1 protein changes using the AroCell TK 210 ELISA in an acute myeloid leukemia (AML) xenograft model during 5-fluoruracil treatment
Authors: Jagarlamudi Kiran Kumar , Jayaraman Ramesh , Babu Sundaresh , Shaw Martin , Eriksson Staffan 
Published: September 2020

Background Thymidine kinase 1 (TK1) is a cytosolic enzyme involved in DNA precursor synthesis and it is up-regulated in proliferating cells. Serum TK1 is an established biomarker for prognosis and therapy monitoring of malignancies. However, commercial TK1 enzyme activity assays have limitations for their use in xenograft models as they cross-react with TK1 activity from the host. The AroCell TK 210 ELISA is specific for human TK1 and offers the opportunity to measure the release of TK1 from human xenografts free from the background of TK1 release from the host (mouse). Here we studied the changes in serum TK1 protein levels using the AroCell TK 210 ELISA in a xenograft model during 5-fluorouracil (5FU) treatment of Acute Myeloid Leukemia (AML).

Experimental Procedures Human MV-4-11 leukemic cells from ATCC were cultured with 95% O2 and 5% CO2 at 37°C and in IMD medium (Sigma) supplemented with 10% FBS (HI media) containing 4mmol/L L-glutamine, 5 ng/mL GM-CSF and 1% penicillin and streptomycin. The cells were harvested during exponential growth and injected subcutaneously into the left flank of athymic BALB/c nude mice 8-10 weeks old. The mice were divided into controls that received no therapy (n=8) and an active group receiving 5FU (n=8). The treatment was initiated when the average tumor volume reached 50-100 mm3. Tumor bearing mice were treated with PBS (control) or 5-FU (active group 10 mg/kg, once daily) for three weeks. Serum samples (70-80 µL) were collected before treatment initiation, during treatment (once weekly for 3 weeks) and a final termination. Serum samples were stored at -80°C and TK1 protein levels were determined with the AroCell TK 210 ELISA. All the animal experiments were performed at TheraIndx life sciences Pvt Ltd, India.

Results The tumor volumes were measured post-implantation of cells every 3 days throughout the study. There was a significant difference (p&lt;0.05) in the mean tumor volume between 5-FU treated (5-FU) (108.75± 36.3 mm3) and untreated controls (294.63± 50.17 mm3) at the end of treatment. There was a significant reduction in the tumor volume from 2nd week onwards in 5-FU treated mice up to termination (4th week) compared to control mice. TK1 protein concentrations increased significantly from the 2nd week onwards in 5-FU treated mice (0.42± 0.19 µg/L) in comparison to controls (0.1± 0.02 µg/L) in spite of the decrease in tumor volume in response to treatment. No cross-reactivity of TK 210 ELISA with mouse TK1 was observed.

Conclusions This study is the first evaluation of TK 210 ELISA as a biomarker for monitoring therapy with anticancer drugs in an AML xenograft model. The changes in TK1 protein levels were significant enough to monitor the response of the xenograft to 5FU therapy in this animal model. Furthermore, the use of the AroCell TK 210 ELISA in xenograft models may enable more accurate measurement of the anti-cancer drug effects on cell proliferation and these results encourage further applications of TK 210 ELISA in drug development projects.

Citation Format: Kiran Kumar Jagarlamudi, Ramesh Jayaraman, Sundaresh Babu, Martin Shaw, Staffan Eriksson. Evaluation of TK1 protein changes using the AroCell TK 210 ELISA in an acute myeloid leukemia (AML) xenograft model during 5-fluoruracil treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3130.