The Impact of the Low Molecular Weight Heparin Tinzaparin on the Sensitization of Cisplatin-Resistant Ovarian Cancers-Preclinical In Vivo Evaluation in Xenograft Tumor Models.

Resistance formation of tumors against chemotherapeutics is the major obstacle in clinical cancer therapy. Although low molecular weight heparin (LMWH) is an important component in oncology referring to guideline-based antithrombotic prophylaxis of tumor patients, a potential interference of LMWH with chemoresistance is unknown. We have recently shown that LMWH reverses the cisplatin resistance of A2780cis human ovarian cancer cells in vitro. Here we address the question whether this LMWH effect is also valid under in vivo conditions. Therefore, we established tumor xenografts of A2780 and cisplatin resistant A2780cis cells in nude mice and investigated the impact of daily tinzaparin applications (10 mg/kg BW) on anti-tumor activity of cisplatin (6 mg/kg BW, weekly) considering the tumor growth kinetics. Intratumoral platinum accumulation was detected by GF-AAS. Xenografts of A2780 and A2780cis cells strongly differed in cisplatin sensitivity. As an overall consideration, tinzaparin co-treatment affected the response to cisplatin of A2780cis, but not A2780 tumors in the later experimental time range. A subgroup analysis confirmed that initially smaller A2780cis tumors benefit from tinzaparin, but also small A2780 xenografts. Tinzaparin did not affect cisplatin accumulation in A2780cis xenografts, but strongly increased the platinum content in A2780, obviously related to morphological differences in both xenografts. Although we cannot directly confirm a return of A2780cis cisplatin resistance by tinzaparin, as shown in vitro, the present findings give reason to discuss heparin effects on cytostatic drug efficiency for small tumors and warrants further investigation.

Heparin antagonizes cisplatin resistance of A2780 ovarian cancer cells by affecting the Wnt signaling pathway.

Low molecular weight heparin (LMWH), the guideline based drug for prophylaxis and treatment of cancer-associated thrombosis, was recently shown to sensitize cisplatin resistant A2780cis human ovarian cancer cells for cisplatin cytotoxicity upon 24 h pretreatment with 50 µg × mL-1 of the LMWH tinzaparin in vitro, equivalent to a therapeutic dosage. Thereby, LMWH induced sensitization by transcriptional reprogramming of A2780cis cells via not yet elucidated mechanisms that depend on cellular proteoglycans. Here we aim to illuminate the underlying molecular mechanisms of LMWH in sensitizing A2780cis cells for cisplatin. Using TCF/LEF luciferase promotor assay (Top/Flash) we show that resistant A2780cis cells possess a threefold higher Wnt signaling activity compared to A2780 cells. Furthermore, Wnt pathway blockade by FH535 leads to higher cisplatin sensitivity of A2780cis cells. Glypican-3 (GPC3) is upregulated in A2780cis cells in response to LMWH treatment, probably as counter-regulation to sustain the high Wnt activity against LMWH. Hence, LMWH reduces the cisplatin-induced rise in Wnt activity and TCF-4 expression in A2780cis cells, but keeps sensitive A2780 cells unaffected. Consequently, Wnt signaling pathway appears as primary target of LMWH in sensitizing A2780cis cells for cisplatin toxicity. Considering the outstanding role of LMWH in clinical oncology, this finding appears as promising therapeutic option to hamper chemoresistance.

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.