Low molecular weight heparin tinzaparin antagonizes cisplatin resistance of ovarian cancer cells.

Low molecular weight heparin (LMWH) is routinely used for antithrombotic treatment of cancer patients. Preclinical- and clinical data suggest that LMWH has beneficial effects for cancer patients beyond the prevention of thrombosis, i.e. by inhibiting metastasis. It is, however, unclear whether heparin has an impact on the efficiency of chemotherapy in cancer patients. Here we show that a therapeutic dosage of LMWH tinzaparin reverses cisplatin resistance of A2780cis human ovarian cancer cells to the level of sensitive cells. This novel activity of tinzaparin is associated with intense transcriptional reprogramming. Our gene expression profiling experiments revealed that 3776 genes responded to tinzaparin treatment. For this reason tinzaparin has a complex impact on diverse biological processes. We discovered that tinzaparin inhibits the expression of genes that mediate cisplatin resistance of A2780cis cells. In contrast tinzaparin induced the expression of genes that antagonize drug resistance. This activity of tinzaparin is mediated by cell surface proteoglycans, since enzymatic cleavage of heparan sulfates prevented the reversal of cisplatin resistance. These data indicate that cell surface heparan sulfate proteoglycans play an important role for chemotherapy resistance. The results of this study shed a new light on LMWH application in cancer therapy and suggest tinzaparin as promising treatment option of ovarian cancer patients in combination with anticancer drugs. Future clinical trials are needed to validate these findings.

How liposomal Cisplatin overcomes chemoresistance in ovarian tumour cells.

The frequent development of cellular resistance to cisplatin in cancer patients is a serious limitation for clinical drug therapy. However, cisplatin resistance is incompletely understood. We have shown that cisplatin-resistant A2780 ovarian cancer cells (A2780cis) can efficiently be eliminated by liposomal cisplatin, which displayed similar cytotoxicity towards both A2780 and A2780cis cells. This may, at least in part, be related to a higher intracellular accumulation of the drug within the resistant cells after liposomal entry. However, the superior cytotoxicity of the liposomal drug was not reflected by DNA platination. This suggests a more complex mode of action of liposomal cisplatin, most likely affecting different signaling pathways. To gain insight into the resistance gene signature, a whole-genome gene expression analysis was performed for A2780cis cells, untreated or treated with half-minimal inhibitory concentration (IC50) of free and liposomal cisplatin. Strong differences in the functional networks affected by free and liposomal cisplatin became evident. p53 was identified as a key factor directing differences in the apoptotic processes. While free cisplatin induced the intrinsic pathway of apoptosis, liposomal cisplatin induced expression of genes of DNA damage pathways and of the extrinsic pathway of apoptosis. These predictions from gene expression data were confirmed at the protein and function level. This sheds new light on liposomal drug carrier approaches in cancer and suggests liposomal cisplatin as a promising strategy for the treatment of cisplatin-resistant ovarian carcinoma.

Overcoming chemotherapy resistance of ovarian cancer cells by liposomal cisplatin: molecular mechanisms unveiled by gene expression profiling.

Previously we reported that liposomal cisplatin (CDDP) overcomes CDDP resistance of ovarian A2780cis cancer cells (Krieger et al., Int. J. Pharm. 389, 2010, 10-17). Here we find that the cytotoxic activity of liposomal CDDP is not associated with detectable DNA platination in resistant ovarian cancer cells. This suggests that the mode of action of liposomal CDDP is different from the free drug. To gain insight into mechanisms of liposomal CDDP activity, we performed a transcriptome analysis of untreated A2780cis cells, and A2780cis cells in response to exposure with IC50 values of free or liposomal CDDP. A process network analysis of upregulated genes showed that liposomal CDDP induced a highly different gene expression profile in comparison to the free drug. p53 was identified as a key player directing transcriptional responses to free or liposomal CDDP. The free drug induced expression of essential genes of the intrinsic (mitochondrial) apoptosis pathway (BAX, BID, CASP9) most likely through p38MAPK activation. In contrast, liposomal CDDP induced expression of genes from DNA damage pathways and several genes of the extrinsic pathway of apoptosis (TNFRSF10B-DR5, CD70-TNFSF7). It thus appears that liposomal CDDP overcomes CDDP resistance by inducing DNA damage and in consequence programmed cell death by the extrinsic pathway. Predictions from gene expression data with respect to apoptosis activation were confirmed at the protein level by an apoptosis antibody array. This sheds new light on liposomal drug carrier approaches in cancer and suggests liposomal CDDP as promising strategy for the treatment of CDDP resistant ovarian carcinomas.