Abstract 4122: Ras GTPase activating like protein (IQGAP1) in human acute myelogenous leukemia.
Authors: Sahasrabudhe Deepak M. , Bechelli Jeremy 
Published: August 2014

Background and Significance: Prognosis of acute myelogenous leukemia in patients over the age of 60 is poor. Recent recognition that the process of transformation utilizes a limited number of common pathways as decsribed by Hanahan and Weinberg provided the impetus to validating and extending previously published observation that immunization with normal human white blood cells (WBC) whose surface charge had been modified in vitro elicited an antibody response that cross-reacted against a broad range of leukemias (MB Sahasrabudhe Nature 1971).

Specific Aim: Isolation and molecular characterization of a shared antigenic moiety from human leukemia cells.

Methods: Peripheral blood was collected from healthy volunteers in ACD tubes. Red blood cells were removed by dextran sedimentation and hypotonic shock lysis. The WBCs were incubated with fluorodinitrobenzene (FDNB) at 104 molecules per cell for 12-15 minutes at room temperature. Three rabbits were immunized with FDNB-treated cells. A control rabbit was immunized with sham-treated cells. Immune sera were collected and complement was inactivated. The sera were absorbed against untreated WBCs from normal healthy donors. Absorbed immune sera were tested against leukemia cells lines (agglutination and flowcytometry) and clinical leukemia samples by Western blotting after SDS-PAGE. Antigens from whole cell lysates and membrane prep were immunoprecipitated using IgG adsorbed on protein A/G agarose beads. Liquid chromatography and mass spectrometry (LC-MS) analysis of the immunoprecipitated was performed.

Results: Sera from experimental rabbits immunized with modified WBCs agglutinated leukemia cell lines (titers 1:256 to 512) whereas serum from the rabbit immunized with untreated WBCs did not. Sera from experimental rabbits also showed greater intensity of staining of leukemia cell lines by flowcytometry. Western blots of whole cell lysates and membrane preps from clinical acute myelogenous leukemia samples and normal bone marrow were probed with pre-immune serum and immune sera from the control rabbit as well as one of the experimental rabbits. Several bands recognized by the serum from experimental rabbits, immunized with FDNB-treated WBCs, but not by serum from control rabbit, immunized with sham-treated WBCs. LC-MS of the immunoprecipitated material revealed IQGAP1 and major vault transporter proteins as being differentially recognized.

Conclusion and Future Directions: Immunization of rabbits with normal peripheral blood WBCs that had been incubated with nanogram quantities of FDNB elicited an antibody response that identified IQGAP1 and major vault transporter proteins as shared feature in human acute myelogenous leukemias. Investigation of the role of IQGAP1, a critical regulator of multiple cellular functions, in human acute myelogenous leukemia will be undertaken.

Citation Format: Deepak M. Sahasrabudhe, Jeremy Bechelli. Ras GTPase activating like protein (IQGAP1) in human acute myelogenous leukemia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4122. doi:10.1158/1538-7445.AM2013-4122