ELAS1 induces apoptotic death in adenocarcinoma DU145 and squamous-cell carcinoma SAS cancer cells, but not in normal KD cells.

Toshihiro Uchihashi,Kohshiro Fukushima,Yusuke Yabuno,Kaori Ota,Hiroshi Nojima,Shouichi Ohno,Yoko Naito,Norikazu Yabuta,Mikihiko Kogo

doi:10.18632/oncotarget.20696

Abstract

We previously reported that an ELAS1 peptide containing 29 amino acids induces apoptotic death in U2OS human osteosarcoma cells following DNA double-strand break insults. Here, we show that ELAS1 also caused apoptosis in prostate adenocarcinoma DU145 cells and tongue squamous-cell carcinoma SAS cells. ELAS1 appears to be safe because it induced apoptosis only in cancer cells, not in normal KD cells. Because the effect of ELAS1 is dependent on increased stability of p53 and enhanced phosphorylation of p53-S46, we exogenously expressed wild-type p53 protein to fully promote ELAS1-mediated induction of apoptosis in SAS cells. Interestingly, simultaneous expression of Myc-ELAS1 and FLAG-p53 mediated by an internal ribosome entry site efficiently induced apoptosis in SAS cells. Moreover, we prepared a recombinant adenovirus that simultaneously expressed Myc-ELAS1 and FLAG-p53. This adenovirus also killed SAS cells, as determined by a cell viability assay, in the presence of camptothecin, an inducer of DNA double-strand breaks. Moreover, nude mice harboring Myc-ELAS1-expressing SAS cells lived longer than mice harboring Myc-vector-expressing SAS cells, suggesting the usefulness of ELAS1 in vivo. Notably, Cy5-tagged ELAS1-t, which contained only ten amino acids, also efficiently induced apoptosis in both DU145 and SAS cells, suggesting the usefulness of ELAS1-t as a peptide. Taken together, our results suggest that ELAS1 is therapeutically useful as a peptide drug.

Highlights

Radiation therapy (RT) using concentrated beams of ionizing radiation (IR) is curative in various cancers [1]
We previously showed that the ELAS1 peptide efficiently causes apoptosis in human osteosarcoma U2OS cells through inhibition of the Cyclin G1 (CycG1)-B’γ association, leading to stabilization and activation of p53 [9]
Western blot (Wb) analysis confirmed the successful construction of these DU145/Tet-On cells expressing Myc-vector or Myc-ELAS1 in a Doxdependent manner (Figure 1A)

Summary

Introduction

Radiation therapy (RT) using concentrated beams of ionizing radiation (IR) is curative in various cancers [1]. IR selectively kills cancer cells because it induces DNA lesions, including DNA double-strand breaks (DSBs). An adjuvant that helps to kill cancer cells with a much lower dose of IR and the same therapeutic effectiveness has been sought [3]. Some types of chemotherapeutic drugs, such as camptothecin (CPT) and irinotecan, induce DSBs in cancer cells [4, 5]. CPT causes the persistence of www.impactjournals.com/oncotarget single-strand DNA breaks by stabilizing topoisomerase I-DNA cleavage complexes [6]. CPT is a natural product isolated from a Chinese tree (Camptotheca acuminate) and has been used as a Chinese herbal medicine to treat cancer [7]. Because CPT has severe side effects, numerous CPT analogues such as irinotecan (CamptosarTM) have been synthesized and are presently used in cancer chemotherapy [8]

Objectives

Methods

Results

Conclusion