NLK Is a Novel Therapeutic Target for PTEN Deficient Tumour Cells

Ana M Mendes-Pereira,Alan Ashworth,Christopher J Lord,Giuseppe Viglietto

doi:10.1371/journal.pone.0047249

Ana M Mendes-Pereira, Alan Ashworth + Show 2 more

Open Access

https://doi.org/10.1371/journal.pone.0047249

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Abstract

PTEN (Phosphatase and tensin homolog) is a tumour suppressor gene commonly defective in human cancer, and is thus a potentially important therapeutic target. Targeting tumour suppressor loss-of-function is possible by exploiting the genetic concept of synthetic lethality (SL). By combining the use of isogenic models of PTEN deficiency with high-throughput RNA interference (RNAi) screening, we have identified Nemo-Like Kinase (NLK) inhibition as being synthetically lethal with PTEN deficiency. This SL is likely mediated by the transcription factor FOXO1 (Forkhead box O1), an NLK substrate, as the selectivity of NLK gene silencing for PTEN deficient cells can be reversed by FOXO1 knockdown. In addition, we provide evidence that PTEN defective cells targeted by NLK gene depletion undergo senescence, suggesting that NLK function is critical for the continued proliferation of PTEN deficient cells. Taken together, these data provide new insight into the potential of targeting of NLK to treat a range of tumourigenic conditions characterised by PTEN deficiency.

Highlights

Loss of function mutations in the tumour suppressor gene PTEN or lack of PTEN expression have both been observed in a wide range of human tumours [1]
We have shown that PTEN deficiency is synthetically lethal with inhibition of PARP1 [3], and effect predicted from the proposed role of PTEN in maintaining genomic stability [2]
PTEN deficiency in this model was achieved by targeting a truncating mutation to both copies of PTEN at exon 2, with the resultant mutant alleles encoding an ostensibly dysfunctional PTEN mutant protein consisting of only the 24 N-terminal aminoacids [6,7]

Summary

Introduction

Loss of function mutations in the tumour suppressor gene PTEN or lack of PTEN expression have both been observed in a wide range of human tumours [1]. We reverse-transfected PTEN wild type and null human tumour cell lines with a short-interfering (si)RNA library arrayed in 96-well plates and measured effects of each siRNA on cell proliferation using CellTiter-GloH reagent (Promega) five days after transfection. Cells were transfected with siRNA as per the HTS and surviving fractions calculated from CellTiterGlo luminescence measurements five days later.

Results

Conclusion