Osteosarcoma tissues and cell lines from patients with differing serum alkaline phosphatase concentrations display minimal differences in gene expression patterns

Abstract

Serum alkaline phosphatase (ALP) concentration is a prognostic factor for osteosarcoma in multiple studies, although its biological significance remains incompletely understood. To determine whether gene expression patterns differed in osteosarcoma from patients with differing serum ALP concentrations, microarray analysis was performed on 18 primary osteosarcoma samples and six osteosarcoma cell lines from dogs with normal and increased serum ALP concentration. No differences in gene expression patterns were noted between tumours or cell lines with differing serum ALP concentration using a gene-specific two-sample t-test. Using a more sensitive empirical Bayes procedure, defective in cullin neddylation 1 domain containing 1 (DCUN1D1) was increased in both the tissue and cell lines of the normal ALP group. Using quantitative PCR (qPCR), differences in DCUN1D1 expression between the two groups failed to reach significance. The homogeneity of gene expression patterns of osteosarcoma associated differing serum ALP concentrations are consistent with previous studies suggesting serum ALP concentration is not associated with intrinsic differences of osteosarcoma cells.

Keywords: cell signalling; comparative oncology; genetics; oncology; tumour biology.

Figure 1

(A) The serum ALP concentration (mean ± SEM) for the normal (112.8 ± 16.1 U L⁻¹) and increased (273 ± 62.6 U L⁻¹) serum ALP samples used in this study. (B) Dot-plot representing the serum ALP concentration relative to the upper-limit of normal for individual samples from the normal and increased serum ALP groups.

Figure 2

(A) The median overall survival time for dogs with osteosarcoma associated with normal (n = 9) and increased (n = 9) serum ALP concentration was 240 and 147 days, respectively (P = 0.2). (B) The median survival time for dogs with osteosarcoma associated with normal (n = 7) and increased (n = 6) serum ALP concentration undergoing amputation and adjuvant chemotherapy was 240 and 208 days, respectively (P = 0.4). serum ALP concentration was 240 and 147 days (P = 0.2), respectively (Fig. 2A). If limited to only the 13 dogs undergoing amputation and receiving cytotoxic chemotherapy, the overall median survival time was 240 days. When assessing the OS time for these dogs according to serum ALP concentration, the median OS time for dogs with normal and increased serum ALP concentration was 240 and 208 days (P = 0.4), respectively (Fig. 2B).

Figure 3

Microarray analysis identifies DCUN1D1 as being differentially expressed between canine osteosarcoma primary tumour in dogs with normal and increased serum ALP concentration at diagnosis. Data presented as the mean (solid bar in box), inter-quartile range (box), and overall range (whiskers) of DCUN1D1 expression on microarray analysis.

Figure 4

The difference in relative gene expression of DCUN1D1 between primary canine osteosarcoma cell lines associated with normal (n = 3) and increased (n = 3) serum ALP concentration fails to reach significance (P = 0.16). Data presented as the mean (solid bar in box), inter-quartile range (box), and overall range (whiskers) of relative expression of DCUN1D1 with qPCR.