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Control of breast tumor cell growth using a targeted cysteine protease inhibitor
1Division of Developmental Biology, Nemours Research Programs, Alfred I. duPont Hospital for Children, Wilmington, Delaware 19803, USA.
Abstract:
The purpose of this study was to determine whether inhibition of lysosomal proteolysis could be used to selectively inhibit proliferation of tumor cells. The lysosomal cysteine protease inhibitor 9-fluorenylmethyloxycarbonyl-tyrosylalanyl-diazomethane was found to inhibit growth of the breast cancer cell lines SK-Br-3 and MCF-7. A humanized monoclonal antibody (huMAb 4D5) directed against the extracellular domain of p185HER2 specifically inhibited growth of the SK-Br-3 cells, which overexpress this antigen. The antibody and inhibitor together showed enhanced inhibition of growth of the SK-Br-3 cells only. When the protease inhibitor was radiolabeled and conjugated to the antibody (huMAb 4D5-125I-Tyr-Ala-CHN2) it was selectively bound to and taken up by the SK-Br-3 cell line. The conjugated inhibitor was delivered and targeted to cathepsin B and an unidentified protein of Mr 39,000 in the SK-Br-3 cells. Internalization of huMAb 4D5-125I-Tyr-Ala-CHN2 and inhibitor labeling of the proteins were temperature-dependent processes. huMAb 4D5-Tyr-Ala-CHN2 was significantly more effective in inhibiting proliferation of SK-Br-3 cells than the inhibitor-free analogue but was ineffective against MCF-7 cells. The results in this report show that targeting of cysteine protease inhibitors can selectively control tumor cell growth and that targeted cysteine protease inhibitors could prove valuable in the development of novel anticancer immunotherapies.
Insights
Targeting lysosomal proteolysis with cysteine protease inhibitors selectively inhibits tumor cell growth. Conjugating inhibitors to antibodies enhances this effect, offering a novel approach for cancer immunotherapy.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Lysosomal proteolysis plays a role in cellular processes.
- Targeting specific cellular pathways is a strategy in cancer therapy.
- Cysteine proteases are implicated in tumor cell proliferation.
Purpose of the Study:
- To investigate if inhibiting lysosomal proteolysis can selectively target tumor cell proliferation.
- To evaluate the efficacy of a cysteine protease inhibitor and a monoclonal antibody against breast cancer cell lines.
- To assess the potential of targeted drug delivery for cancer treatment.
Main Methods:
- Utilized a lysosomal cysteine protease inhibitor (9-fluorenylmethyloxycarbonyl-tyrosylalanyl-diazomethane).
- Employed a humanized monoclonal antibody (huMAb 4D5) targeting p185HER2.
- Developed a radiolabeled antibody-inhibitor conjugate (huMAb 4D5-125I-Tyr-Ala-CHN2) for targeted delivery.
- Assessed inhibition of breast cancer cell lines (SK-Br-3 and MCF-7) proliferation.
Main Results:
- The cysteine protease inhibitor inhibited growth of both SK-Br-3 and MCF-7 cells.
- huMAb 4D5 selectively inhibited SK-Br-3 cells overexpressing p185HER2.
- The antibody-inhibitor conjugate demonstrated enhanced and selective inhibition of SK-Br-3 cell growth.
- The conjugate targeted cathepsin B and an unidentified 39 kDa protein within SK-Br-3 cells.
- Targeted conjugate was more effective than the free inhibitor in SK-Br-3 cells.
Conclusions:
- Targeting cysteine protease inhibitors can achieve selective tumor cell growth control.
- Antibody-drug conjugates offer a promising strategy for targeted cancer therapy.
- This approach holds potential for developing novel immunotherapies against cancer.