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A clone of cancer cells is resistant to vincristine, doxorubicin, and dactinomycin but not to methotrexate and alkylat. agents. Mechanism of resistance?
a. absence of superoxide dismutase
b. altered DNA polymerase
c. enhanced drug transport out of the cell
d. inability to form polyglutames
e. increase DNAse


absence of superoxide dismutase


Let Me put an end to this debate once and for all, b/c this inaccurate info. is deterring people from getting these questions right on the test. I don't like it when people post wrong answers on these forums. Anyway, I digress...

The answer is Multi-drug resistance gene. Multidrug resistance is mediated by a cell membrane glycoprotein (P-glycoprotein). It's an energy-dependent efflux pump that actively kicks out a variety of cytotoxic agents from cells including natural products such as plant alkaloids (vincas, podophyllotoxins, paclitaxel), anthracyclines (doxorubicin, daunorubicin) and some synthetic agents (e.g. mitoxantrone). P-glycoprotein is normally expressed in tissues such as the lining of the gut, the brush border of the kidney and the choroid plexus. Cancer cells can spontaneously turn on these genes and get busy w/ metastases.

Good Luck w/ boards, I take mine in two Weeks.

Peace Up, A-town down.

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