Determination of O6-Methylguanine in dried blood spot of breast cancer patients after cyclophosphamide administration

Yahdiana Harahap; Athalia Theda Tanujaya; Farhan Nurahman; Aurelia Maria Vianney; Denni Joko Purwanto

doi:10.1016/j.heliyon.2021.e07558

Determination of O⁶-Methylguanine in dried blood spot of breast cancer patients after cyclophosphamide administration

Heliyon. 2021 Jul 13;7(7):e07558. doi: 10.1016/j.heliyon.2021.e07558. eCollection 2021 Jul.

Authors

Yahdiana Harahap^{1

2}, Athalia Theda Tanujaya¹, Farhan Nurahman¹, Aurelia Maria Vianney¹, Denni Joko Purwanto³

Affiliations

¹ Bioavailability/Bioequivalence Laboratory, Faculty of Pharmacy, Universitas Indonesia, Depok 16424, West Java, Indonesia.
² Faculty of Pharmacy, Republic of Indonesia Defense University, Bogor, 16810, Indonesia.
³ Dharmais Cancer Hospital, West Jakarta, 11420, Jakarta, Indonesia.

Abstract

Cyclophosphamide is a nitrogen mustard class of drugs that are often used in cancer chemotherapy. However, the use of Cyclophosphamide in high doses over a long period has been shown to increase the risk of developing secondary cancer. This can be indicated by the formation of mutagenic DNA adducts, such as O⁶-Methylguanine. Therefore, this adduct can be used as a biomarker for secondary cancer in patients receiving Cyclophosphamide. Bio sampling was carried out by using the Dried Blood Spot (DBS) method, followed by DNA extraction by using QIAamp DNA mini kit, and acid hydrolysis to obtain O⁶-Methylguanine. Analysis of O⁶-Methylguanine was performed by using the UPLC-MS/MS instrument with the conditions developed by Vianney, Harahap, & Suryadi (2021). Partial validation was carried out before the analysis. The results obtained from the calibration curve, accuracy, and precision validation test met the FDA requirements. The analysis method was then implemented in 16 breast cancer patients who received the Cyclophosphamide regimen. The O⁶-Methylguanine was successfully detected and quantified in all of the samples in the range of 0.55-6.66 ng/mL. It shows that the O⁶-Methylguanine accumulation in cancer patients receiving Cyclophosphamide is very likely to occur and the analysis method proposed by Vianney, Harahap, & Suryadi (2021) is potential to be used for Therapeutic Drug Monitoring in this group of patients.

Keywords: Cyclophosphamide; Dried blood spot (DBS); O6-Methylguanine; Secondary cancer; UPLC-MS/MS.