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Decreased expression and function of alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein
M C Luna1, A Ferrario, N Rucker
1Clayton Ocular Oncology Center, Childrens Hospital Los Angeles 90027, USA.
Abstract:
Parental and photodynamic therapy (PDT)-resistant mouse, radiation-induced fibrosarcoma cell lines were evaluated using mRNA differential display in an attempt to identify unique transcripts. We detected one transcript that was consistently present in the parental cells but absent in PDT-resistant cells. The transcript was cloned, sequenced, and identified as alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein (alpha-2 MR/LRP). Northern and Western immunoblot analysis confirmed that receptor expression was present in the parental cell line but barely detectable in PDT-resistant cells. Functionality of the receptor was evaluated by exposing cells to Pseudomonas exotoxin A. alpha-2 MR/LRP is responsible for Pseudomonas exotoxin A internalization, and only the parental cells exhibited toxin-mediated cytotoxicity. The binding and endocytosis of activated alpha-2 macroglobulin and lipoproteins by alpha-2 MR/LRP are consistent with modulating uptake and localization of photosensitizers. Our results demonstrate that PDT-resistant murine tumor cells exhibit minimal alpha-2 MR/LRP activity and suggest that this receptor plays a role in PDT sensitivity by modulating photosensitizer uptake and/or subcellular localization.
Insights
Photodynamic therapy (PDT) resistance in mouse fibrosarcoma cells is linked to reduced alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein (alpha-2 MR/LRP) activity. This suggests alpha-2 MR/LRP influences photosensitizer uptake and PDT sensitivity.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- Photodynamic therapy (PDT) is a cancer treatment utilizing photosensitizers activated by light.
- Resistance to PDT can limit treatment efficacy, necessitating investigation into underlying molecular mechanisms.
- Identifying factors contributing to PDT resistance is crucial for improving therapeutic outcomes.
Purpose of the Study:
- To identify unique transcripts in parental versus PDT-resistant murine fibrosarcoma cells.
- To investigate the role of alpha-2 macroglobulin receptor/low density lipoprotein receptor-related protein (alpha-2 MR/LRP) in PDT resistance.
- To determine if alpha-2 MR/LRP expression and function correlate with photosensitizer uptake and PDT sensitivity.
Main Methods:
- mRNA differential display to identify unique transcripts between cell lines.
- Cloning, sequencing, and identification of the differentially expressed transcript as alpha-2 MR/LRP.
- Northern and Western immunoblot analysis to confirm receptor expression levels.
- Functional assays using Pseudomonas exotoxin A to assess receptor activity.
- Evaluation of photosensitizer uptake and localization.
Main Results:
- A transcript, identified as alpha-2 MR/LRP, was present in parental cells but absent in PDT-resistant cells.
- PDT-resistant cells showed minimal alpha-2 MR/LRP expression and reduced functionality.
- Cells expressing alpha-2 MR/LRP were sensitive to Pseudomonas exotoxin A, indicating receptor activity.
- alpha-2 MR/LRP activity correlated with the uptake and localization of photosensitizers.
Conclusions:
- PDT-resistant murine tumor cells exhibit significantly reduced alpha-2 MR/LRP activity.
- alpha-2 MR/LRP plays a role in PDT sensitivity, likely by modulating photosensitizer uptake and subcellular localization.
- Targeting alpha-2 MR/LRP could be a strategy to overcome PDT resistance in certain cancers.