Author(s): Bareford LM, Avaritt BR, Ghandehari H, Nan A, Swaan PW
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Abstract PURPOSE: In breast cancer, a significant decrease in riboflavin (RF) serum levels and increase in RF carrier protein occurs, indicating a potential role of RF in disease progression. To evaluate RF's ability to serve as a targeting agent, mitomycin C (MMC)-conjugated N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers were synthesized and targeted to the RF internalization pathway in human breast cancer cells. METHODS: Competitive uptake studies were used to determine specificity of RF-targeted conjugates, and an MTT assay established the IC₅₀ for the conjugates. Endocytic mechanisms were investigated by confocal microscopy. RESULTS: Studies revealed a high-affinity endocytic mechanism for RF-specific internalization of fluorescently-labeled conjugates in both MCF-7 and SKBR-3 cells, whereas folic acid-mediated endocytosis showed high specificity only in SKBR-3 cells. MMC internalization was significantly higher following nontargeted and RF-targeted MMC-conjugate administration compared to that of free MMC. Cytotoxic analysis illustrated potent IC₅₀ values for RF-targeted MMC conjugates similar to free MMC. Maximum nuclear accumulation of MMC resulted from lysosomal release from RF-targeted and nontargeted MMC-conjugates following 6 h incubations, unlike that of free MMC seen within 10 min. CONCLUSION: Targeting polymer-MMC conjugates to the RF internalization pathway in breast cancer cells enabled an increase in MMC uptake and nuclear localization, resulting in potent cytotoxic activity.
This article was published in Pharm Res
and referenced in Medicinal Chemistry