Introduction:
"Temozolomide is an alkylating agent that mediates its cytotoxic effect by forming O6-methylguanine (O6-meG) DNA adducts, which during DNA replication pair preferentially with thymidine. These O6-meG:T mispairs
can result in a G-to-A point mutation during a subsequent round of DNA replication but are also substrates for the postreplication mismatch repair pathway, which after a further round of DNA replication leads to apoptosis (1). O6-meG DNA adducts can be repaired by the DNA repair protein O6-alkylguanine-DNA alkyltransferase (MGMT), which removes adducts from the O6 position of guanine by accepting them onto a cysteine residue within its active site. Furthermore, fibroblasts and
bone marrow cells of MGMT knockout mice are significantly more sensitive to the toxic effects of temozolomide than those from MGMT wild-type mice (2).
The protective role of MGMT against the cytotoxic effect of temozolomide has been shown in human cell lines (3) and human xenograft models (4).
MGMT can be inactivated by free guanine base derivatives that have alkyl groups at the O6 position, which act as ‘‘pseudosubstrates.’’ O6-benzylguanine (5) and O6-(4-bromothenyl) guanine (PaTrin-2, Patrin, Lomeguatrib, KuDOS, Cambridge, United Kingdom; ref. 6) have been identified as the most promising MGMT inactivators. Compared with temozolomide used as a single agent, the combination PaTrin-2-temozolomide has been shown to significantly increase tumor growth inhibition in human melanoma
xenografts (7)."
Source:http://mct.aacrjournals.org/content/3/10/1215.full.pdf
Sensitization of a human ovarian cancer cell line totemozolomide by simultaneous attenuation of the Bcl-2 antiapoptotic protein and DNA repair by O6-alkylguanine-DNA alkyltransferase
That is why, and I forgot to tell you that I did a trial with Patrin and DTIC Prior to CTLA-4 Blockage Therapy.
Take Care
Have a Great Weekend!!!!!
Jimmy B
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