Assessment of GM-CSF receptors by real-time RT-PCR on cell lines expressing high and low affinity receptors and their relation to cytotoxic effect of chimeric protein[StxA1-GM-CSF]

Immunotoxins, which are composed of both the cell targeting and the cell killing moieties are the new approach for targeted therapy of human disease. In all immunotoxins that GM-CSF has been used as cell targeting; only cell lines expressing high affinity receptor have been used for cytotoxicity studies. In the present study, various cell lines expressing high and low affinity receptors were used for assessment of the cytotoxic effect of hybrid chimeric protein. The expression of GM-CSF receptor [GM-CSFR] was quantified by real-time RT- PCR. The cell lines K562 and THP1 expressing high affinity receptor and MC-7, PC-3 and DU145 expressing low affinity receptor were used for this study. The chimeric hybrid protein was found to be toxic for various cell lines used in this investigation and cytotoxicity was more effective in cell lines bearing high affinity receptors. Overall, our results showed that the recombinant hybrid protein could have wide range of application on various cancer cell lines even cells bearing low affinity receptors for GM-CSF