Quantifying Intracellular Platinum Accumulation Using Inductively Coupled Mass Spectrometry.

The platinum-based anticancer drug cisplatin and its analog carboplatin are the most used chemotherapeutic agents worldwide. It is estimated that approximately half of all cancer patients are treated with platinum drugs at some point during the therapy regimen. Cisplatin covalently binds to purine nucleobases to form DNA adducts. Cisplatin therapy is faced with two key challenges. First, despite the initial response, many patients develop cisplatin resistance. Reduced cellular accumulation of cisplatin is one common cause of therapy resistance. Second, cisplatin treatment causes general cytotoxicity, leading to severe side effects. Monitoring the subcellular concentration of platinum chemotherapeutics will help yield clinical efficacy with the minimum possible dose. Inductively coupled plasma-mass spectrometry (ICP-MS) is an analytical technique to quantify the elemental composition of various types of liquified bulk samples with high sensitivity. This article describes quantifying cisplatin accumulation in chromatin and total cell lysate using ICP-MS. The method involves treating cells with cisplatin, isolating RNA-free DNA, digesting samples, ICP-MS instrumentation, and data analysis. Although we describe these steps in one cancer cell line, the protocol can be adapted to any cell line or tissue. The protocol should be a valuable resource for investigators interested in accurate measurement of subcellular concentration of platinum and other metallo-drugs. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Cell culture conditions for A2780 cells and cisplatin treatment Basic Protocol 2: Isolating cellular fractions and sample quantitation Basic Protocol 3: Sample digestion, ICP-MS data collection, and analysis.