PIM-1–specific mAb suppresses human and mouse tumor growth by decreasing PIM-1 levels, reducing Akt phosphorylation, and activating apoptosis
Xiu Feng Hu, … , Nancy S. Magnuson, Pei Xiang Xing
Xiu Feng Hu, … , Nancy S. Magnuson, Pei Xiang Xing
Published January 19, 2009
Citation Information: J Clin Invest. 2009;119(2):362-375. https://doi.org/10.1172/JCI33216.
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Research Article Oncology

PIM-1–specific mAb suppresses human and mouse tumor growth by decreasing PIM-1 levels, reducing Akt phosphorylation, and activating apoptosis

Abstract

Provirus integration site for Moloney murine leukemia virus (PIM1) is a proto-oncogene that encodes a serine/threonine kinase with multiple cellular functions. Overexpression of PIM-1 plays a critical role in progression of prostatic and hematopoietic malignancies. Here we describe the generation of a mAb specific for GST–PIM-1, which reacted strongly with most human and mouse cancer tissues and cell lines of prostate, breast, and colon origin but only weakly (if at all) with normal tissues. The mAb binds to PIM-1 in the cytosol and nucleus as well as to PIM-1 on the surface of human and murine cancer cells. Treatment of human and mouse prostate cancer cell lines with the PIM-1–specific mAb resulted in disruption of PIM-1/Hsp90 complexes, decreased PIM-1 and Hsp90 levels, reduced Akt phosphorylation at Ser473, reduced phosphorylation of Bad at Ser112 and Ser136, and increased cleavage of caspase-9, an indicator of activation of the mitochondrial cell death pathway. The mAb induced cancer cell apoptosis and synergistically enhanced antitumor activity when used in combination with cisplatin and epirubicin. In tumor models, the PIM-1–specific mAb substantially inhibited growth of the human prostate cancer cell line DU145 in SCID mice and the mouse prostate cancer cell TRAMP-C1 in C57BL/6 mice. These findings are important because they provide what we believe to be the first in vivo evidence that treatment of prostate cancer may be possible by targeting PIM-1 using an Ab-based therapy.

Authors

Xiu Feng Hu, Jie Li, Scott Vandervalk, Zeping Wang, Nancy S. Magnuson, Pei Xiang Xing

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Figure 2

Immunohistochemical staining and Western blot of P9 in tissues and cell lines.

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Immunohistochemical staining and Western blot of P9 in tissues and cell ...
Immunohistochemical staining of normal mouse IgM (A) and P9 (B) in prostate cancer cells DU145, and immunoperoxidase staining of P9 in formalin-fixed tissues of human (C) and mouse (D) prostate cancers, normal human colon (E) and colon cancer (F), and normal lung (G) and lung cancer (H), respectively, are shown. Original magnification, ×400. (I) The western blot analysis of P9 binding to PIM-1 protein in cancer cell lysates shows that P9 reacted with 44-, 33-, and 37-kDa isoforms of PIM-1 in various cancer cell lines, including prostate (PC3, DU145), breast (MCF7), colon (LS174T), and lung cancer (Ben), leukemia (U937, CCRF/CEM, CEM/A7R), and murine prostate cancer (TRAMP-C1). The cell lysates were run on 4%–12% gradient SDS-PAGE gel. The samples were run on same gel but were noncontiguous as indicated by the white lines.