| The major objective of this thesis has been to provide insights into the mode of action of targeted therapies against the two main subsets of human breast cancer cells.; For the ER positive subset we examined the effect of 2-methoxyestradiol (2ME), on MCF-7 and T-47D breast cancer cells. Although 2ME has anti-proliferative and anti-tumerigenic effects, it can also cause cell proliferation at physiological concentrations. We found that the proliferative effect of 2ME was modulated by E2. 2ME was able to inhibit genomic and non-genomic functions of E2. In the absence of E2. 2ME was able to activate non-genomic signaling of Akt through ERalpha. These results call for the selective use of 2ME for ERalpha positive breast cancers.; For the ER-negative subset of breast cancer, our aim was to down-regulate the expression of HER-2 using antisense oligonucleotides (ODN) and curcumin. First, we studied the ability of natural polyamines and their structural analogs to stabilize nucleic acid hybrids comprising of antisense ODN targeted to the HER-2 mRNA. We found that polyamines and their analogs are capable of stabilizing these nucleic acid hybrids, indicating that polyamines may be useful in facilitating the action of antisense ODNs targeted to HER-2 mRNA.; Next, we found that curcumin caused potent inhibition of cell growth and reduced ODC activity, polyamine levels and HER-2 protein levels in HER-2 overexpressing SK-BR-3 cells. Interestingly, curcumin action was partly reversed by blocking the redox pathway using glutathione. Thus, glutathione level is an important factor in action of curcumin in SK-BR-3 cells.; We also explored aspects of gene therapy in developing therapeutics for breast cancer. We found that 22 kDa linear polyethylenimine (PEI) was more efficient in gene delivery than low molecular weight and branched forms. Florescence microscopy indicated 22 kDa PEI-DNA complexes reached the nucleus, whereas 25 kDa branched PEI-DNA complexes remained at the cell membrane/cytoplasm.; In conclusion, our studies on 2ME and curcumin elucidate pathways for their mode of action in two major subsets of breast cancer cells and our studies on nucleic acid stability and PEI provide valuable insights for the design of effective gene therapy strategies. |
