Modulation of tamoxifen sensitivity by antisense Bcl-2 and trastuzumab in breast carcinoma cells

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Ryungsa Kim1, Kazuaki Tanabe, Manabu Emi

  • 1International Radiation Information Center, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan. rkim@hiroshima-u.ac.jp

Cancer
|April 15, 2005
PubMed
Abstract

Insights

Antisense (AS) Bcl-2 enhances tamoxifen (TAM) sensitivity in breast cancer cells more effectively than trastuzumab. This improved sensitivity is linked to Bcl-2 pathway modulation and apoptosis induction.

Area of Science:

  • Oncology
  • Molecular Biology
  • Pharmacology

Background:

  • Overexpression of HER-2 and Bcl-2 proteins is linked to tamoxifen (TAM) resistance in breast cancer.
  • Investigating novel therapeutic strategies to overcome TAM resistance is crucial for improving patient outcomes.

Purpose of the Study:

  • To compare the efficacy of antisense (AS) Bcl-2 with trastuzumab in overcoming TAM resistance in breast carcinoma cell lines.
  • To elucidate the molecular mechanisms underlying TAM sensitivity modulation by AS Bcl-2 and trastuzumab.

Main Methods:

  • In vitro drug sensitivity assays (MTT assay) were performed on breast carcinoma cell lines (ZR-75-1, MDA-MB-453, BT-474).
  • Antisense (AS) Bcl-2 oligonucleotide and trastuzumab were used in combination with TAM.
  • Apoptosis was assessed using TUNEL assay, and gene expression was analyzed via Western blot.

Main Results:

  • AS Bcl-2 demonstrated superior enhancement of TAM sensitivity compared to trastuzumab in HER-2 and Bcl-2 expressing cells.
  • Combination therapy with AS Bcl-2 significantly reduced IC50 values for TAM in ZR-75-1 and BT-474 cell lines.
  • AS Bcl-2 treatment led to down-regulation of Bcl-2 and pAkt, correlating with increased Bax and caspase-3, inducing apoptosis.

Conclusions:

  • AS Bcl-2 is a promising therapeutic agent for overcoming TAM resistance in specific breast cancer subtypes.
  • AS Bcl-2 exhibits a superior ability to modulate signal-transduction pathways involved in breast carcinoma cell survival compared to trastuzumab.

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