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[Inhibitory effect of monoclonal antibody PD4 on Ha-ras transformed cells Rat3-3]
1Beijing Institute for Cancer Research.
Abstract:
McAbPD4 could inhibit the proliferation of transformed cells Rat3-3 with an inhibition rate of 72.3% in vitro. Moreover, McAbPD4 decreased the Rat3-3's colony forming ability on soft agar and tumorigenicity in nude mice. By Flow Cytometry, it was indicated that the inhibitory effect was due to a blockade between G1 and S phase. It was shown by Western Blotting that the McAbPD4-defined antigen was a 40 KD protein, named p40, which was located on the membrane of target cells MGC803 and transformed cells Rat3-3 by immunofluorescence assay. The antigen p40 was highly expressed on Ha-, Ki-, Nb- and Src oncogene transfected cells, but was undetectable or at the best only faintly on cells transformed with mos or raf. The antisense oligonucleotide AS-1 of Ha-ras distinctively inhibited the proliferation of Rat3-3, the level of Ha-ras oncogene product p21 and p40 were decreased by 47.8%, 36.5%, and 52.0%, respectively. The inhibitory effect of AS-1 to GCM3T3 was more marked, each with 54.2%, 47.9% and 65.9%. It is suggested that p40 not only is a tumor-associated antigen, but also a transformation-related cell surface protein, which is closely associated with and might be regulated by the activation of ras or Src oncogene and its product. For the inhibitory effect of McAbPD4 to Rat3-3 cells, it is deduced that p40 might be a growth factor receptor mediating autocrine growth of Ha-ras transformed cells.
Insights
Monoclonal antibody PD4 (McAbPD4) inhibits cancer cell proliferation and tumorigenicity by targeting the p40 protein. This tumor-associated antigen is linked to ras and Src oncogene activation, suggesting its role in cell growth regulation.
Area of Science:
- Molecular Biology
- Oncology
- Immunology
Context:
- Cancer cell proliferation is a hallmark of tumorigenesis, driven by aberrant signaling pathways.
- Identifying specific cell surface proteins involved in oncogene-driven transformation is crucial for targeted therapies.
Purpose:
- To investigate the inhibitory effects of monoclonal antibody PD4 (McAbPD4) on transformed cells.
- To characterize the antigen recognized by McAbPD4 and its association with oncogene activation.
Summary:
- McAbPD4 significantly inhibited the proliferation, soft agar colony formation, and tumorigenicity of Rat3-3 transformed cells.
- Flow cytometry revealed cell cycle arrest between G1 and S phases. Western blotting and immunofluorescence identified a 40 kDa membrane protein, p40, as the target antigen.
- p40 expression was high in cells transfected with Ha-, Ki-, Nb-, and Src oncogenes, but low in mos- or raf-transformed cells. Antisense oligonucleotide AS-1 targeting Ha-ras reduced p21 and p40 levels, suggesting p40 is regulated by ras activation.
Impact:
- p40 is identified as a tumor-associated antigen and a transformation-related cell surface protein potentially regulated by ras/Src oncogene activation.
- The findings suggest p40 may function as a growth factor receptor, mediating autocrine growth in Ha-ras-transformed cells, offering a potential therapeutic target.