Tyrosine kinases expressed in vivo by human prostate cancer bone marrow metastases and loss of the type 1 insulin-like growth factor receptor

Abstract

An important biological feature of prostate cancer (PCa) is its marked preference for bone marrow as a metastatic site. To identify factors that may support the growth of PCa in bone marrow, expression of receptor and nonreceptor tyrosine kinases by androgen-independent PCa bone marrow metastases was assessed. Bone marrow biopsies largely replaced by PCa were analyzed using reverse transcriptase-polymerase chain reaction amplification with degenerate primers that amplified the conserved kinase domain. Sequence analyses of the cloned products demonstrated expression of multiple kinases. Expression of the receptor and nonreceptor tyrosine kinases, alpha platelet-derived growth factor receptor and Jak 1, respectively, was confirmed by immunohistochemistry. In contrast, the type 1 insulin-like growth factor receptor, thought to play a role in PCa development, was lost in metastatic PCa. These results implicate several specific growth factors and signaling pathways in metastatic androgen-independent PCa and indicate that loss of the type 1 insulin-like growth factor receptor contributes to PCa progression.

Figure 1.

Immunohistochemical analyses of αPDGF-R and Jak 1 in metastatic PCa in bone marrow. A: Normal bone marrow stained with αPDGF-R Ab showing strong staining by megakaryocytes (arrow). B: Normal bone marrow stained with Jak 1 Ab showing strong staining in scattered macrophages (arrow). C–E: PCa bone marrow metastases stained with anti-PSA, anti-αPDGF-R, and anti-Jak 1 antibodies, respectively. F: PCa biopsy stained with αPDGF-R antibody after preincubation with the immunizing peptide. Original magnifacation, ×200.

Figure 2.

Immunohistochemical analyses of αPDGF-R and Jak 1 in primary PCa. A and B: Primary PCa stained with αPDGF-R and Jak 1 antibodies, respectively. C and D: Nonneoplastic prostate stained with αPDGF-R and Jak 1 antibodies, respectively. Arrow in D shows basal cell staining. Original magnification ×200.

Figure 3.

Dot blot analysis of tyrosine kinase expression. Replicate dot blots of amplified kinase domains from bone marrow metastases or normal prostate were hybridized with the indicated probes.

Figure 4.

Type 1 IGF-R immunohistochemistry on frozen sections of PCa in prostate and bone marrow metastases. Frozen sections were stained with a monoclonal mouse anti-human type 1 IGF-R. A and B: Low and high power of nonneoplastic prostate. C and D, Low and high power of primary PCa. E and F: metastatic androgen-independent PCa in bone marrow biopsies from two patients. Original magnifications, A, ×100; B, ×200; C, ×200; D–E, ×400.

Figure 5.

Type 1 IGF-R immunohistochemistry on paraffin sections of PCa in prostate and bone marrow metastases. Sections were stained with mouse anti-human type 1 IGF-R mAb, after antigen retrieval. A and B: Low and high power (boxed area) of nonneoplastic prostate; atrophic glands are also present on the right margin of A. C and D: Low and high power (boxed area) of primary PCa. E: Another area of PCa from the same biopsy as in C and D. F: Bone marrow biopsy containing PCa (with some normal marrow elements in lower right corner). Original magnifications, A, ×90; B, D, ×660; C, E, ×140; F, ×420.