Abstract:
Introduction:
Bone Sialoprotein (BSP) is found in mineralized tissues, such as bone, cementum, dentin and mineralized cartilage, where it represents a considerable part of the extracellular matrix.
BSP regulates bone metabolism by directly influencing the activity of osteoblasts and osteclasts.
Lately BSP could also be detected in a multitude of non-mineralized tissues.
A significant correlation between the tissue expression of BSP in tumors and the occurrence of bone metastases could be demonstrated for breast and lung cancer.
The role of BSP for osseous metastases in renal cell carcinoma has not been analyzed up to now.
Aim of this study was, to identify the BSP expression in renal cell carcinomas, according to their type of metastases.
Material and Methods:
Tissue samples of patients with renal cell carcinomas (RCC), who underwent partial resection or nephrectomy were separated into 3 groups, each with 10 patients, who showed either no metastases (group I, 3x T<3, 7x T3), only soft tissue metastases (group II, 2/8) or bone metastases (group III, 3/7) at date of operation.
Immunohistochemical analysis of BSP expression in malign tissue and corresponding renal parenchyma was performed and evaluated with an established semiquantitative scoring system.
BSP expression was described as relative fraction of a maximum and compared towards group membership and clinical data via one way ANOVA.
A linear regression analysis was carried out to test the correlation between malign tissue and renal parenchyma.
Results:
BSP expression could be detected both in malign tissue and renal parenchyma.
Concerning the expression in malign tissue, no significant difference could be found between the 3 groups (200, 191 und 196 for I,II und III, p=0.91).
Surprisingly the corresponding renal parenchyma showed noticeable differences between the 3 groups with 164, 198 und 224 for group I, II and III (p=0.18).
A correlation between the intraindividual expression of malign tissue and renal parenchyma could be found in group I (p=0.05) and II (p=0.04) but not in group III (p=0.36).
RCC staged T3 showed only a little higher BSP expression than those staged T1/2 (202 vs. 179, p < 0.21), while the corresponding parenchyma of T3 tumors showed significantly higher expressions (214 vs. 145, p=0.02). Differences concerning age or gender were not observed.
Conclusion:
This study was able to show a correlation between the expression of BSP and both tumor staging and type of metastases, especially for osseous metastases in RCC.
Alternation of BSP expression could be detected particularly beyond malign tissue and linked to the osseous type of metastases.
Therefore BSP seems to be identified as a parameter, associated with the effects of RCC on the surrounding tissue.
In how far such changes of BSP tissue expression have effects on bone structures and are able to advantage osseous metastases will be subject matter of further studies.
Nevertheless BSP seems to provide a potential marker for understanding the mechanisms of metastatic bone preference and thereby offers a possible point of contact for prevention, diagnostics and therapy in RCC.