Underexpression of tumour suppressor LKB1 in clear cell renal cell carcinoma is common and confers growth advantage in vitro and in vivo
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BACKGROUND: Evidence suggests that dysregulation of energy-sensing pathways closely associates with renal cell carcinoma (RCC) development. The metabolic regulation is largely controlled by 5'-AMP activated protein kinase (AMPK) which is activated through phosphorylation by LKB1. METHODS: The expression of LKB1 was determined by reverse transcription-PCR using 10 clinical clear cell RCC (ccRCC) samples and their adjacent normal renal parenchyma, and by immunohistochemical staining of two tissue microarrays containing 201 ccRCC and 26 normal kidney samples. Expression of LKB1 was knocked down in human ccRCC 786-O cells (shLKB1) and compared with cells expressing scrambled control shRNA (shControl). AMPK signalling, proliferation, invasion, and VEGF secretion was measured. The cells were subcutaneously injected into mice to determine tumour growth in vivo. RESULTS: At the protein and transcript levels, a significant reduction in LKB1 expression in tumour compared with normal tissue was found. In vitro, knockdown of LKB1 resulted in reduced AMPK signalling and increased cellular proliferation, invasion, and VEGF secretion compared with shControl cells. In vivo, growth of shLKB1 ccRCC xenografts in nude mice was significantly increased compared with shControl xenografts. CONCLUSION: Collectively, our results suggest that LKB1 acts as a tumour suppressor in most sporadic cases of ccRCC and that underexpression of LKB1 is a common event in the disease.
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