Abstract
BackgroundLoss of PTEN is involved in tumor progression of several tumor entities including renal cell carcinoma (RCC). During the translation process PTEN generates a number of splice variants, including PTEN-Δ. We analyzed the impact of PTEN-Δ in RCC progression.MethodsIn specimens of RCC patients the expression of PTEN-Δ and PTEN was quantified. The PTEN expressing RCC cell line A498 and the PTEN deficient 786-O cell line were stably transfected with the PTEN-Δ or PTEN transcript. In Caki-1 cells that highly express PTEN-Δ, this isoform was knocked down by siRNA. Cell migration, adhesion, apoptosis and signaling pathways activities were consequently analyzed in vitro.ResultsPatients with a higher PTEN-Δ expression had a longer lymph node metastasis free and overall survival. In RCC specimens, the PTEN-Δ expression correlated with the PTEN expression. PTEN-Δ as well as PTEN induced a reduced migration when using extracellular matrix (ECM) compounds as chemotaxins. This effect was confirmed by knockdown of PTEN-Δ, inducing an enhanced migration. Likewise a decreased adhesion on these ECM components could be shown in PTEN-Δ and PTEN transfected cells. The apoptosis rate was slightly increased by PTEN-Δ. In a phospho-kinase array and Western blot analyses a consequently reduced activity of AKT, p38 and JNK could be shown.ConclusionsWe could show that the PTEN splice variant PTEN-Δ acts similar to PTEN in a tumor suppressive manner, suggesting synergistic effects of the two isoforms. The impact of PTEN-Δ in context of tumor progression should thus be taken into account when generating new therapeutic options targeting PTEN signaling in RCC.
Highlights
Loss of Phosphatase and tensin homolog on chromosome 10 (PTEN) is involved in tumor progression of several tumor entities including renal cell carcinoma (RCC)
We demonstrate that PTEN-Δ is translated in RCC cell lines and analyzed the effect of PTEN-Δ overexpression or silencing on specific steps of tumor progression and metastasis in vitro
In the primary tumor of RCC patients PTEN-Δ expression correlates negatively with tumor progression The expression level of PTEN-Δ and PTEN was examined by Real-Time PCR in a cohort of 71 patients with RCC (Table 1)
Summary
Loss of PTEN is involved in tumor progression of several tumor entities including renal cell carcinoma (RCC). We analyzed the impact of PTEN-Δ in RCC progression. PTEN (Phosphatase and Tensin homolog on chromosome 10) encodes a tumor suppressor protein with dual specific protein and phospholipid phosphatase activity [1]. It is expressed ubiquitously and mediates cellular processes like adhesion, migration, cell survival and apoptosis [2]. We demonstrate that PTEN-Δ is translated in RCC cell lines and analyzed the effect of PTEN-Δ overexpression or silencing on specific steps of tumor progression and metastasis in vitro
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