Down-regulation of ribosomal protein L7A in human osteosarcoma

To explore the expression of ribosomal protein L7A (RPL7A) in osteosarcoma and its correlation with clinical features.

Ribosomal protein L7A mRNA expression was quantified by real-time reverse transcription (RT)-polymerase chain reaction (PCR) in 47 specimens from osteosarcoma, 8 from normal bone tissues and 12 from benign bone lesion tissues. Expression of RPL7A mRNA was also detected in human osteosarcoma cell line MG-63. The relationship between RPL7A mRNA expression and clinicopathological factors was statistically analyzed. The immunoblotting pattern of RPL7A was also analyzed in 20 osteosarcomas, 8 normal bone and 8 benign bone tissues.

Ribosomal protein L7A mRNA expression in osteosarcoma samples was significantly down-regulated compared with that in samples from normal bone (P < 0.001) and benign bone lesion tissues (P < 0.001). Low expression of RPL7A mRNA was also found in osteosarcoma cell line MG-63. Low expression of RPL7A mRNA was significantly associated with increased serum level of alkaline phosphatase (ALP, P = 0.008), but was not correlated with other clinicopathological parameters including sex, age, serum lactate dehydrogenase (LDH), tumor location, histological type, histological grading, lung metastasis and overall survival. Interestingly, survival analysis suggested low RPL7A mRNA expression was a significant poor prognostic indicator for overall survival in patients with high grade lesion developed lung metastasis at the time of diagnosis of the primary osteosarcoma (P < 0.05). On western blot, reduced expression of RPL7A protein was observed in osteosarcoma samples (n = 20) compared with normal bone (n = 8) (P < 0.001) and benign bone tissues (n = 8) (P < 0.001).

Under-expression of RPL7A may be involved in the carcinogenesis of osteosarcoma. Loss of RPL7A expression may be associated with poor survival of osteosarcoma patients with lung metastasis.