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Host factors in metastasis: immunostimulatory action of retinoids
Abstract:
Many host factors contribute to the death of cells shed from cancers and with many immunogenic tumors immune control is decisive in determining the incidence of metastasis. Although an aromatic analogue of retinoic acid did not affect the growth of nonimmunogenic carcinomas or sarcomas it slowed the tumor growth of immunogenic cancers but only if they were grown in immunocompetent hosts. A working hypothesis is that retinoids enhance the magnitude of a T-cell dependant host response to the tumor and it is this that causes the inhibition of growth. If the animals are rendered incapable of evoking a T-cell response then retinoids are unable to influence tumor growth.
Insights
Retinoids slow the growth of immunogenic tumors in immunocompetent hosts by enhancing T-cell responses. This effect is lost in hosts unable to mount a T-cell mediated immune response, highlighting the importance of host immunity in cancer control.
Area of Science:
- Immunology
- Oncology
- Pharmacology
Background:
- Host factors and immune control significantly influence cancer metastasis.
- Tumor growth is influenced by the host's immune status and tumor immunogenicity.
Purpose of the Study:
- To investigate the effect of retinoids on tumor growth in different host immune environments.
- To elucidate the role of T-cell mediated immune responses in retinoid-induced tumor growth inhibition.
Main Methods:
- Administration of an aromatic retinoic acid analogue to mice bearing immunogenic and nonimmunogenic tumors.
- Assessment of tumor growth in immunocompetent hosts versus hosts with impaired T-cell responses.
Main Results:
- Retinoids slowed the growth of immunogenic tumors but not nonimmunogenic ones.
- This inhibitory effect was observed only in immunocompetent hosts.
- Retinoids failed to influence tumor growth in hosts incapable of T-cell responses.
Conclusions:
- Retinoids enhance T-cell dependent host anti-tumor responses, leading to tumor growth inhibition.
- The efficacy of retinoids in controlling immunogenic tumors relies on the host's intact T-cell mediated immunity.