Synthesis, Cytotoxicity, and Apoptosis-Associated Cell Death Activity of an Isatin-Containing Pyrimidine-Derived Cu(II) Complex.

A Cu(II) complex derived from a pyrimidine with the isatin group was synthesized and tested for its cytotoxic effects on A549 lung cancer and MCF-7 breast cancer cell lines, as well as its effects on apoptosis-associated cell death and cell cycle regulation in A549 cells. To evaluate cytotoxicity, MTT assays were performed at 24, 48, and 72 h, and IC50 values were computed using the four-parameter logistic (4PL) model. Selectivity indices were determined using the human primary dermal fibroblast (HDFa) cell line, and apoptosis-related cell death was preliminarily assessed by flow cytometry with Annexin V/PI double staining. Cell cycle distribution was analyzed by propidium iodide staining. The Cu(II) complex showed time-dependent cytotoxicity in both cancer cell lines. The IC50 values for A549 cells were 31.20, 17.68, and 11.33 μM at 24, 48, and 72 h, whereas MCF-7 cells had values of 70.41, 32.58, and 23.34 μM, showing increased sensitivity. Selectivity indices showed the compound was two to four times more selective against cancer cells than healthy cells. Flow cytometry analysis at the 48-h IC50 concentration revealed apoptosis-associated cell death, with a combined early apoptotic, late apoptotic, and necrotic cell population of approximately 60%, including a substantial necrotic fraction, suggesting that cell death may involve mixed mechanisms at this concentration. Cell cycle analysis revealed significant accumulation in the G2/M phase (26% ± 2.3%, p < 0.001), consistent with cell cycle arrest. In conclusion, the synthesized Cu(II) complex demonstrated substantial cytotoxic activity, apoptosis-associated cell death, and G2/M phase arrest in A549 and MCF-7 cell lines, suggesting its potential as a candidate anticancer agent warranting further mechanistic investigation.