Effect of Id1 knockdown on formation of osteolytic bone lesions by prostate cancer PC3 cells in vivo

Abstract

The formation of osteolytic bone lesions is a key process for osteolytic cancer to metastasize to the bone and is under the control of a set of transcription factors. Recently, the inhibitor of differentiation 1 (Id1) has been linked with angiogenesis, tumorigenesis, metastasis and bone formation. However, the function of Id1 during the process of bone destruction caused by cancer in vivo has not yet been elucidated. We, therefore, examined whether and how Id1 affects the ability of cancer to form osteolytic lesion in vivo. The study used a lentiviral vector overexpressing short hairpin RNA (shRNA) targeting Id1 gene. PC3 cells, a prostate cancer cell line, were transduced with Id1 shRNA or negative control (NC) shRNA before implantation in BALB/c mice. Cells were implanted in a tibial injection model. Tumor formation in bone was monitored by X-ray. The relationship between parathyroid hormone-related protein (PTHrP), an osteolytic factor, and Id1 was analyzed by using immunohistochemistry in tissue sections from osteolytic lesion of the BALB/c mice. Our results showed that Id1 shRNA delivery to PC3 cells by lentivirus caused efficient and stable Id1 gene silencing. In the intratibial model, PC3 cells produced primarily osteolytic lesions in the bone. Eleven of 14 mice in Id1 shRNA group but only 4 of 14 mice in the NC shRNA group developed osteolytic lesions with cortical destruction at 4th week. Mice treated with Id1 shRNA had larger tumor volume in the bone and larger cortical destruction. The expression of PTHrP protein in PC3 cells was not affected by Id1 knockdown in vivo. These results indicate that Id1 may down-regulate the ability of PC3 cells to form osteolytic lesions in vivo and the signal pathway needs to be further investigated.

Mouse models for studying prostate cancer bone metastasis

“…Negative Negative Osteolytic Intratibial injection, Intrafemoral injection, intracardiac injection, Intravenous injection into human bone implanted animals Kaighn et al, 7 Nemeth et al, 5 Chu et al, 8 Wu et al, 9 Zhang et al 10…”

Identification of Fibulin‐1 as a Human Bone Marrow Stromal (HS‐5) Cell‐Derived Factor That Induces Human Prostate Cancer Cell Death

“…Results from previous studies showed that one specific bone marrow stromal cell line, HS-5, secreted soluble factor(s) (HS-5 DF) that induce PCa apoptosis and neuroendocrine differentiation (NED) [8,10]. No significant effect could be seen in PC3 cell line, which primarily caused osteolytic bone lesion [8,36]. However, the phenomenon was found in an isogenic LNCaP progression model including LNCaP, C4-2, and C4-2B cell lines, which were shown to cause osteosclerotic bone lesion corresponding to PCa bone metastasis in PCa patients and animal models [8,15,37,38].…”

Inhibitor of Differentiation 1 (Id1) in Cancer and Cancer Therapy

“…Network analysis indicates that Id1 promotes cancer morphology, cell cycle and epithelial to mesenchymal transition by influencing AP1, tnf, tgfbeta, PdgfBB and estradiol pathways [66]. Intriguingly, study also showed that Id1 could down-regulate the ability of PC3 cells to form osteolytic lesions in vivo, although in the same study it was observed that knockdown of Id1 in PC3 cells inhibited the proliferation of cancer cells in vitro [67]. While evidence also suggests that Id1 is a key factor in promoting cancer metastasis to lungs [68], the discrepancy of microenvironment in different sites may be the cause.…”