Depending on the cellular context and malignancy grade, 17-AAG has been shown to facilitate arrest in all checkpoints of the cell cycle, as for example, in human malignant pleural mesothelioma (G1 or G2/M block) [20] and breast cancer cells (G1 block) overexpressing HER2 [21]. This evidence concerns the gene ERBB2 and malignant pleural mesothelioma.