Cytotoxic activity and inhibition of tumor cell invasion by derivatives ofa chemically modified tetracycline CMT-3 (COL-3)

Tetracyclines such as chlortetracycline and doxycycline with antimicrobial activity were reported to possess cytostatic and cytotoxic activity against mammalian tumor cells, often at high doses. Non-antimicrobial chemically m odified tetracyclines (CMTs), with limited systemic toxicity bur with signi ficant tumor cell toxicity and antimetastatic activity, art: attractive for long term treatment for cancer. We recently reported uni such CMT, 6-deoxy ,6-demethyl 4-dedimethylamino tetracycline (CMT-3) is a potent anti-tumor a nd anti-metastatic drug. Here we report on the anti-cell proliferation and anti-invasive activity or five nitro derivatives of CMT-3 (CMT-3N). All the five CMT-3Ns (CMT-302, CMlT-303, CMT-306, CMT-308 and CMT-316) inhibited i n vitro cell proliferation of pi-estate cancer cells. The 50% growth inhibi tion concentration (IC50) of CMT-3Ns was similar to that of CMT-3. Although CMT-3 was by far the most potent anti-cell proliferation drug, all CMT-3Ns except CMT-303 and CMT-308 had similar anti-cell proliferation activity (I C50: 2.5 -5.7 mug/ml). IC(50)s for CMT-303 and CMT-308 were similar to 8.1 and -12.4 mug/ml, respectively. Activity against tumor cell invasion was te sted in vitro using the Matrigel invasion assay. All CMT-3Ns had similar an ti- invasive activity. While cytotoxic activity of CMT-3 was strongly assoc iated with cell death-effector caspase activation, mitochondrial permeabliz ation and apoptosis, the CMT-3Ns weakly induced apoptosis and did not activ ate Caspase-3. However, the CMT-3Ns were able to induce mitochondrial perme abilization. This dichotomous mechanism of cytotoxic activity of CMTs may h ave significance in their selection for clinical application.