High expression of KCa3.1 in patients with clear cell renal carcinoma predicts high metastatic risk and poor survival

PLoS One. 2015 Apr 7;10(4):e0122992. doi: 10.1371/journal.pone.0122992. eCollection 2015.

Abstract

Background: Ca2+-activated K+ channels have been implicated in cancer cell growth, metastasis, and tumor angiogenesis. Here we hypothesized that high mRNA and protein expression of the intermediate-conductance Ca2+-activated K+ channel, KCa3.1, is a molecular marker of clear cell Renal Cell Carcinoma (ccRCC) and metastatic potential and survival.

Methodology/principal findings: We analyzed channel expression by qRT-PCR, immunohistochemistry, and patch-clamp in ccRCC and benign oncocytoma specimens, in primary ccRCC and oncocytoma cell lines, as well as in two ccRCC cell lines (Caki-1 and Caki-2). CcRCC specimens contained 12-fold higher mRNA levels of KCa3.1 than oncocytoma specimens. The large-conductance channel, KCa1.1, was 3-fold more highly expressed in ccRCC than in oncocytoma. KCa3.1 mRNA expression in ccRCC was 2-fold higher than in the healthy cortex of the same kidney. Disease specific survival trended towards reduction in the subgroup of high-KCa3.1-expressing tumors (p<0.08 vs. low-KCa3.1-expressing tumors). Progression-free survival (time to metastasis/recurrence) was reduced significantly in the subgroup of high-KCa3.1-expressing tumors (p<0.02, vs. low-KCa3.1-expressing tumors). Immunohistochemistry revealed high protein expression of KCa3.1 in tumor vessels of ccRCC and oncocytoma and in a subset of ccRCC cells. Oncocytoma cells were devoid of KCa3.1 protein. In a primary ccRCC cell line and Caki-1/2-ccRCC cells, we found KCa3.1-protein as well as TRAM-34-sensitive KCa3.1-currents in a subset of cells. Furthermore, Caki-1/2-ccRCC cells displayed functional Paxilline-sensitive KCa1.1 currents. Neither KCa3.1 nor KCa1.1 were found in a primary oncocytoma cell line. Yet KCa-blockers, like TRAM-34 (KCa3.1) and Paxilline (KCa1.1), had no appreciable effects on Caki-1 proliferation in-vitro.

Conclusions/significance: Our study demonstrated expression of KCa3.1 in ccRCC but not in benign oncocytoma. Moreover, high KCa3.1-mRNA expression levels were indicative of low disease specific survival of ccRCC patients, short progression-free survival, and a high metastatic potential. Therefore, KCa3.1 is of prognostic value in ccRCC.

Publication types

  • Clinical Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Carcinoma, Renal Cell / metabolism*
  • Carcinoma, Renal Cell / mortality*
  • Carcinoma, Renal Cell / pathology
  • Cell Line, Tumor
  • Disease-Free Survival
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Intermediate-Conductance Calcium-Activated Potassium Channels / biosynthesis*
  • Kidney Neoplasms / metabolism*
  • Kidney Neoplasms / mortality*
  • Kidney Neoplasms / pathology
  • Male
  • Middle Aged
  • Neoplasm Metastasis
  • Neoplasm Proteins / biosynthesis*
  • Survival Rate

Substances

  • Intermediate-Conductance Calcium-Activated Potassium Channels
  • KCNN4 protein, human
  • Neoplasm Proteins

Grants and funding

MR was supported by the “Region Syddanmark”, by intramural funding of the University Hospital Odense and by the Foundation of Arvid Nielsson. RK and AO were supported by the Deutsche Forschungsgemeinschaft (KO1899/10-1 to RK), Government of Aragon (GIPASC-B105), and the Fondo de Investigación Sanitaria (Red HERACLES RD12/0042/0014). Aida Oliván Viguera was also funded by the European Community (FP7-PEOPLE-CIG-321721). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.