In vitro sensitivity of Kaposi's sarcoma cells to various chemotherapeutic agents including acyclic nucleoside phosphonates

New Indole Tubulin Assembly Inhibitors Cause Stable Arrest of Mitotic Progression, Enhanced Stimulation of Natural Killer Cell Cytotoxic Activity, and Repression of Hedgehog-Dependent Cancer

We designed 39 new 2-phenylindole derivatives as potential anticancer agents bearing the 3,4,5-trimethoxyphenyl moiety with a sulfur, ketone, or methylene bridging group at position 3 of the indole and with halogen or methoxy substituent(s) at positions 4-7. Compounds 33 and 44 strongly inhibited the growth of the P-glycoprotein-overexpressing multi-drug-resistant cell lines NCI/ADR-RES and Messa/Dx5. At 10 nM, 33 and 44 stimulated the cytotoxic activity of NK cells. At 20-50 nM, 33 and 44 arrested >80% of HeLa cells in the G2/M phase of the cell cycle, with stable arrest of mitotic progression. Cell cycle arrest was followed by cell death. Indoles 33, 44, and 81 showed strong inhibition of the SAG-induced Hedgehog signaling activation in NIH3T3 Shh-Light II cells with IC50 values of 19, 72, and 38 nM, respectively. Compounds of this class potently inhibited tubulin polymerization and cancer cell growth, including stimulation of natural killer cell cytotoxic activity and repression of Hedgehog-dependent cancer.

Interleukin-1 beta increases the BCL-2/BAX ratio in Kaposi's sarcoma cells

Interleukin-1 (IL-1) is a multifunctional cytokine known to act as a growth factor for AIDS-KS cells. In addition to its mitogenic effects, we found that IL-1 induced the protection of KS cells from apoptotic death induced by serum deprivation in a dose-dependent manner. AIDS-KS cells as well as cells derived from iatrogenic and sporadic KS exhibited a similar response to IL-1, which stresses the key role of this cytokine in the pathogenesis of KS regardless of its epidemiological form. Using both an immunohistochemical and an immunoblot approach, we found that IL-1 increased the expression of Bcl-2 and decreased that of Bax, while having no effect on the expression of Bclx(L), Fas and CD40. The effects of IL-1 were inhibited by IL-1ra, suggesting that imbalance between these two counter-acting cytokines may contribute to the altered accumulation of KS spindle cells. Our findings may provide a link between KS cell escape from apoptosis and the immune dysregulation known to be associated with KS.

Antiproliferative and apoptotic effects of iron chelators on human cervical carcinoma cells

OBJECTIVE

Cervical carcinoma is a human papillomavirus (HPV)-associated cancer for which treatment options still mainly rely on surgical procedures, with or without adjuvant radiotherapy and chemotherapy. As iron may participate in the pathogenesis of viral infections and cancer in several ways, the present study was designed to investigate the effect of iron chelation on HPV-16- and HPV-18-positive cervical carcinoma cell lines.

METHODS

Desferrioxamine and deferiprone, two chemically unrelated iron chelators, were used to investigate the effect of iron chelation on SiHa and HeLa cells. Proliferation was investigated by cells counts, by [(3)H]thymidine uptake assay, and by immunostaining with Ki-67 and proliferating cell nuclear antigen (PCNA). Apoptosis was determined by morphological analysis, by a TUNEL assay, and by flow cytometry detecting FITC-conjugated annexin-V.

RESULTS

Desferrioxamine and deferiprone induced a time- and dose-dependent inhibition of SiHa and HeLa cell growth. The inhibition of cell growth was associated with a decrease in the expression of both stable and total PCNA and Ki-67, a proliferation marker whose expression may predict survival in uterine cervical carcinoma. TUNEL assay, flow cytometry with annexin-V-fluorescein, and morphological analysis indicated that iron chelation also induced a time- and dose-dependent apoptosis of both cell lines. This apoptotic effect was prevented by the addition of exogenous iron.

CONCLUSION

These results show that iron chelation inhibits the growth and induces the apoptosis of HPV-positive carcinoma cells. This suggests that iron chelators may represent a potential therapeutic approach for the management of cervical carcinoma.

Potent inhibition of hemangiosarcoma development in mice by cidofovir

The acyclic nucleoside phosphonate analogue cidofovir is a broad-spectrum anti-DNA virus agent, which also possesses potent inhibitory activity against various tumors associated with papillomaviruses in animal models and patients. Moreover, we recently described the potent inhibition of polyomavirus (PyV)-induced hemangioma formation in rats by cidofovir. This activity could not be explained by an antiviral mechanism. We have now evaluated the effect of cidofovir on the growth of hemangiosarcomas originating from PyV-transformed (PV/2b/35) cells, which do not produce polyomavirus. In vitro, cidofovir proved to be cytostatic for PV/2b/35 cells at a 50% cytostatic concentration (CC(50)) of 2.3 microg/ml. At cidofovir concentrations > or =20 microg/ml, cytotoxicity due to induction of apoptosis was observed. In vivo, intratumoral therapy with cidofovir, at 100 mg/kg 3 times a week, completely inhibited the development and even caused regression of established PV/2b/35 hemangiosarcomas in nude mice. Five days after the start of treatment, few proliferating cells were noted in the cidofovir-treated tumors, whereas control tumors were characterized by high expression of proliferating cell nuclear antigen (PCNA). Moreover, cidofovir induced apoptosis in the hemangiosarcomas, as evidenced by Tunel (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) staining. Also after intraperitoneal administration, cidofovir afforded a prominent protection against the growth of intraperitoneally or intracerebrally inoculated hemangiosarcoma cells in SCID mice. In conclusion, cidofovir possesses a direct antitumor activity, which is mediated by induction of tumor cell apoptosis. Cidofovir should be further explored for its potential in the treatment of fast-growing vascular tumors, like hemangiomas and hemangiosarcomas.