Cadherin-11 in Renal Cell Carcinoma Bone Metastasis

<div><p>Bone is one of the common sites of metastases from renal cell carcinoma (RCC), however the mechanism by which RCC preferentially metastasize to bone is poorly understood. Homing/retention of RCC cells to bone and subsequent proliferation are necessary steps for RCC cells to colonize bone. To explore possible mechanisms by which these processes occur, we used an <i>in vivo</i> metastasis model in which 786-O RCC cells were injected into SCID mice intracardially, and organotropic cell lines from bone, liver, and lymph node were selected. The expression of molecules affecting cell adhesion, angiogenesis, and osteolysis were then examined in these selected cells. Cadherin-11, a mesenchymal cadherin mainly expressed in osteoblasts, was significantly increased on the cell surface in bone metastasis-derived 786-O cells (Bo-786-O) compared to parental, liver, or lymph node-derived cells. In contrast, the homing receptor CXCR4 was equivalently expressed in cells derived from all organs. No significant difference was observed in the expression of angiogenic factors, including HIF-1α, VEGF, angiopoeitin-1, Tie2, c-MET, and osteolytic factors, including PTHrP, IL-6 and RANKL. While the parental and Bo-786-O cells have similar proliferation rates, Bo-786-O cells showed an increase in migration compared to the parental 786-O cells. Knockdown of Cadherin-11 using shRNA reduced the rate of migration in Bo-786-O cells, suggesting that Cadherin-11 contributes to the increased migration observed in bone-derived cells. Immunohistochemical analysis of cadherin-11 expression in a human renal carcinoma tissue array showed that the number of human specimens with positive cadherin-11 activity was significantly higher in tumors that metastasized to bone than that in primary tumors. Together, these results suggest that Cadherin-11 may play a role in RCC bone metastasis.</p></div

Immunohistochemical staining of human RCC specimens with anti-Cad11 antibody.

<p>(A) Representative image of primary RCC; (B) Representative image of bone metastatic RCC.</p

Message levels of angiogenic and osteolytic factors in 786-O RCC cell lines.

<p>Quantitative PCR for the message levels of angiogenic factors <i>HIF-1α</i> (A), <i>VEGF</i> (B), <i>Ang1</i> (C), <i>Tie-2</i> (D) and <i>c-Met</i> (E), and osteolytic factors <i>PTHrP</i> (F) and <i>IL-6</i> (G) in the four 786-O cell lines. Data were expressed as folds of parental 786-O cells and the values were the Mean ± S.E. *: <i>p</i><0.05; **: <i>p</i><0.01 as compared to parental 786-O cells.</p

Cad11 expression in human primary RCC and bone metastatic RCC specimens.

<p>Staining of human RCC samples for cadherin-11.</p><p>*: chi-square analysis.</p

Generation of organ-tropic 786-O RCC cells.

<p>(A) Parental 786-O RCC cells were labeled with luciferase and GFP. (B) Images of bioluminescence of mice at indicated time point after intracardiac injection with parental 786-O cells. (C) 786-O cells derived from liver, lymph node and bone, were GFP-positive.</p

Expression of Cad11 in 786-O cell lines derived from metastases to various organs.

<p>(A) Quantitative PCR for the message levels of <i>Cad11</i> in the four 786-O cell lines. (B) Western blotting for the protein levels of Cad11 in four 786-O cell lines. Upper panel: A representative image of Western blot. Lower panel: Quantification of band density using Image J software. Data were expressed as folds of parental 786-O cells and the values were the Mean ± S.E. n = 5. *: <i>p</i><0.05; **: <i>p</i><0.01 as compared to parental 786-O cells. (C) FACS for surface expression of Cad11 in the four 786-O cell lines. Data were expressed as percentage of gated cells. (D) Immunofluorescence staining of cells with anti-Cad11 antibody. P, Parental 786-O; Liv, Liv-786-O; LN, LN-786-O, and Bo, Bo-786-O RCC cells.</p

Effect of Cad11 on cell proliferation and migration of Bo-786-O cells.

<p>(<b>A</b>) Proliferation and migration of parental and bone-derived 786-O cells. Left: Western blot of Cad11 protein. Middle: Cell proliferation. Right: Cell migration. A representative image of cell migration and the quantification of cells that migrated to the other side of migration inserts were shown. Values for migration were expressed as the average of migrated cells per microscope field (X100). (B) Effect of Cad11 knockdown on the proliferation and migration of Bo/shCont and Bo/shCad11 cells.</p

Dual inhibition of IR/IGF-1R and SFK decreases tumor growth <i>in vitro</i> more effectively than single pathway inhibition does.

<p>(A) PC-3 or LNCaP cells were cultured for 96 hours with and without dasatinib (DSA; 100 nM) and BMS-754807 (BMS-807; 2 µM for PC-3 and 0.5 µM for LNCaP cells), alone and in combination, and cell numbers were determined as described in the methods. (B) PC-3 and LNCaP cells were incubated for 24 hours with and without DSA (100 nM) and BMS-754807 (5 µM for PC-3 and 1 µM for LNCaP cells), alone and in combination, and cell cycle staining after 24 hours was performed using propidium iodide. (C) PC-3 cells were incubated for 48 hours with and without DSA (100 nM) and BMS-754807 (2 µM), alone and in combination, and the percentage of apoptotic cells was determined by flow cytometric analysis of annexin-V staining. (D)Left: cell cycle staining with propidium iodide in PC-3–shIGF-1R cells. Right: PC-3–shIGF-1R and control cells were incubated for 48 hours with and without DSA (100 nM), and the percentage of apoptotic cells was determined by flow cytometric analysis of annexin-V staining. All experiments were performed in triplicate. *<i>P</i><0.05; N.S. not significant.</p

Modulation of IGF-1–induced Akt1 and Akt2 phosphorylation in PC-3 cells by dasatinib (DSA) and BMS-754807 (BMS-807).

<p>(A) PC-3 cells were serum starved for 72 hours and then pre-incubated for 2 hours with BMS-754807 at either 2 µM or 5 µM, with dasatinib at 100 nM, or with both agents. After 2 hours, the cells were stimulated with 50 ng/mL recombinant human IGF-1 (rhIGF-1) for 3 minutes. Next, protein was harvested and the (phospho)-proteins IGF-1R, Src, and Akt were determined by western blot (WB). Vinculin was used as the loading control. (B and C) PC-3 cells were stimulated with DSA (100 nM) and BMS-754807 (5 µM) as above, and then the cells were harvested and immunoprecipitated for Akt1 (B) or Akt2 (C), followed by immunoblotting for phospho-Akt. (D) PC-3 cells were treated as in (A), and western blot was run for S6 and phospho-S6.</p

Dasatinib (DSA) and BMS-754807 (BMS-807) decrease intratibial bone destruction and tumor formation and modulate bone turnover markers.

<p>Bone-destructive PC3-MM2 cells were injected intratibially in nude mice. Following treatment with dasatinib, BMS-754807 alone and combined, the mice were euthanized, and x-rays and computed tomographic (CT) scanning of the long bones were done (control, n = 10; dasatinib, n = 9; BMS-754807, n = 9; combination, n = 8). Blood was collected for serum bone turnover markers. (A) The degree of bone destruction was blindly graded in a semiquantitative fashion based on x-rays from all mice. The graph displays the proportion of high-grade lesions (i.e., 2 or 3) in each treatment group. * <i>P</i><0.05 combination vs. dasatinib only. (B) Representative CT scans (top) and x-rays (bottom) from the mice in each group. Arrows and numbers indicate the lesion site and the grade of bone destruction. (C and D) Serum levels of murine alkaline phospatase (C) and N-telopeptide (D) were determined by ELISA. Bars indicates SEM. * <i>P</i><0.05.</p