In vitro Cytotoxic Activities of the Oral Platinum(IV) Prodrug Oxoplatin and HSP90 Inhibitor Ganetespib against a Panel of Gastric Cancer Cell Lines

Abstract

Gastric cancer exhibits a poor prognosis and is the third most common cause of cancer death worldwide. Chemotherapy of metastatic gastric cancer is based on combinations of platinum drugs and fluoropyrimidines, with added agents. Oxoplatin is a stable oral platinum(IV) prodrug which is converted to a highly active tetrachlorido(IV) complex under acidic conditions. In the present work, we studied the cytotoxic effects of oxoplatin against a panel of four gastric cancer cell lines in vitro. Furthermore, the role of HSP90 in chemoresistance of these lines was investigated using the specific inhibitor ganetespib. The KATO-III, MKN-1, MKN-28, MKN-45 lines were used in MTT chemosensitivity, cell cycle and apoptosis assays. KATO-III is a signet ring diffuse cell type, MKN-1 an adenosquamous primary, MKN-28 a well-differentiated intestinal type and the MKN-45 a poorly differentiated, diffuse type gastric carcinoma line. Cytotoxicity was tested in MTT assays and intracellular signal transduction with proteome profiler Western blot arrays. Interactions of platinum drugs and ganetespib were calculated with help of the Chou-Talalay method. The prodrug oxoplatin revealed low activity against the four gastric cancer cell lines, whereas the platinum tetrachlorido(IV) complex and cisplatin gave IC50 values of 1-3 µg/ml with increasing chemoresistance observed in the order of MKN-1, KATO-III, MKN-28 to MKN-45. With exception of KATO-III and MKN-28/oxoplatin, all other cell lines featured marked synergistic toxicity with clinically achievable concentrations of ganetespib. Oral administration of a platinum agent such as oxoplatin would be of great value for patients and care providers alike. These results suggest that the oncogene-stabilizing HSP90 chaperone represents an important mediator of chemoresistance in gastric cancer. Ganetespib reduced the phosphorylation of p53, Akt1/2/3 and PRAS40, as well as of WNK1, a kinase which regulates intracellular chloride concentrations. Intracellular chloride was reported to control proliferation of gastric cancer cell lines. Expression of MUC1 was not downregulated in contrast to the expression of CAIX, a prognostic marker in gastric cancer. In conclusion, the HSP90 inhibitor ganetespib synergizes with platinum anticancer drugs and modulates intracellular signal transduction in direction of a less proliferative and aggressive phenotype.

CX-5461-inspired monofunctional platinum RNA polymerase I selective inhibitors with selective lethality in BRCA1-deficient cancer cells

“…Platinum-based agents, such as cisplatin, can also elevate intracellular ROS levels. 37 To evaluate whether ROS production contributed to the cell-killing process of P1-Q1 and P1-Q2 , the intracellular ROS production levels were determined by fluorescence microscopy observation using a DCFH-DA probe. As shown in Fig.…”

Diagnostic, clinicopathologic, therapeutic and prognostic value of Plasma Heat Shock Protein 90 levels in patients with advanced Gastrointestinal Carcinoma

“…HSP70/HSP90-organizing protein may protect GC cells from fluorouracil chemotherapy in an autocrine manner [18]. The HSP90 inhibitor synergizes with platinum and regulates the proliferation and invasion of GC cell lines [19]. Increased HSP90 or lysine demethylase 5B can facilitate the recruitment of X-ray repair cross complement 1 to repair DNA damaged by platinum, and inhibition of HSP90 can reverse chemoresistance in GC [20].…”

Selected platinum complexes in standard and modern anti-cancer therapies

“…It has also been found that it inhibits the growth of neoplastic tumors more than cisplatin and may weaken the process of distant metastases [85]. The cytotoxic properties of oxoplatin have been observed in vitro in neoplastic cells of the pancreas, colon, prostate and stomach [85,88]. However, the mechanism of action of this compound has, as yet, not been fully determined.…”