Hyper-phosphorylation of sequestosome-1 distinguishes resistance to cisplatin in patient derived high grade serous ovarian cancer cells

Elizabeth V. Nguyen, Kaisa Huhtinen, Young Ah Goo, Katja Kaipio, Noora Andersson, Ville Rantanen, Johanna Hynninen, Riitta Lahesmaa, Olli Carpen, David R. Goodlett*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Platinum-resistance is a major limitation to effective chemotherapy regimens in high-grade serous ovarian cancer (HGSOC). To better understand the mechanisms involved we characterized the proteome and phosphoproteome in cisplatin sensitive and resistant HGSOC primary cells using a mass spectrometry-based proteomic strategy. PCA analysis identified a distinctive phosphoproteomic signature between cisplatin sensitive and resistant cell lines. The most phosphorylated protein in cisplatin resistant cells was sequestosome-1 (p62/SQSTM1). Changes in expression of apoptosis and autophagy related proteins Caspase-3 and SQSTM1, respectively, were validated by Western blot analysis. A significant increase in apoptosis in the presence of cisplatin was observed in only the sensitive cell line while SQSTM1 revealed increased expression in the resistant cell line relative to sensitive cell line. Furthermore, site-specific phosphorylation on 20 amino acid residues of SQSTM1 was detected indicating a hyper-phosphorylation phenotype. This elevated hyper-phosphorylation of SQSTM1 in resistant HGSOC cell lines was validated with Western blot analysis. Immunofluoresence staining of s28-pSQSTM1 showed inducible localization to autophagosomes upon cisplatin treatment in the sensitive cell line while being constitutively expressed to autophagosomes in the resistant cell. Furthermore, SQSTM1 expression was localized in cancer cells of clinical high-grade serous tumors. Here, we propose hyper-phosphorylation of SQSTM1 as a marker and a key proteomic change in cisplatin resistance development in ovarian cancers by activating the autophagy pathway and influencing down-regulation of apoptosis.

Original languageEnglish (US)
Pages (from-to)1377-1392
Number of pages16
JournalMolecular and Cellular Proteomics
Issue number7
StatePublished - Jul 2017

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Molecular Biology


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