title: The voltage gated Ca(2+)-channel Cav3.2 and therapeutic responses in breast cancer.
abstract: BACKGROUND
  Understanding the cause of therapeutic resistance and identifying new biomarkers in breast cancer to predict therapeutic responses will help optimise patient care. Calcium (Ca(2+))-signalling is important in a variety of processes associated with tumour progression, including breast cancer cell migration and proliferation. Ca(2+)-signalling is also linked to the acquisition of multidrug resistance. This study aimed to assess the expression level of proteins involved in Ca(2+)-signalling in an in vitro model of trastuzumab-resistance and to assess the ability of identified targets to reverse resistance and/or act as potential biomarkers for prognosis or therapy outcome.
  
  
  METHODS
  Expression levels of a panel of Ca(2+)-pumps, channels and channel regulators were assessed using RT-qPCR in resistant and sensitive age-matched SKBR3 breast cancer cells, established through continuous culture in the absence or presence of trastuzumab. The role of Cav3.2 in the acquisition of trastuzumab-resistance was assessed through pharmacological inhibition and induced overexpression. Levels of Cav3.2 were assessed in a panel of non-malignant and malignant breast cell lines using RT-qPCR and in patient samples representing different molecular subtypes (PAM50 cohort). Patient survival was also assessed in samples stratified by Cav3.2 expression (METABRIC and KM-Plotter cohort).
  
  
  RESULTS
  Increased mRNA of Cav3.2 was a feature of both acquired and intrinsic trastuzumab-resistant SKBR3 cells. However, pharmacological inhibition of Cav3.2 did not restore trastuzumab-sensitivity nor did Cav3.2 overexpression induce the expression of markers associated with resistance, suggesting that Cav3.2 is not a driver of trastuzumab-resistance. Cav3.2 levels were significantly higher in luminal A, luminal B and HER2-enriched subtypes compared to the basal subtype. High levels of Cav3.2 were associated with poor outcome in patients with oestrogen receptor positive (ER+) breast cancers, whereas Cav3.2 levels were correlated positively with patient survival after chemotherapy in patients with HER2-positive breast cancers.
  
  
  CONCLUSIONS
  Our study identified elevated levels of Cav3.2 in trastuzumab-resistant SKBR3 cell lines. Although not a regulator of trastuzumab-resistance in HER2-positive breast cancer cells, Cav3.2 may be a potential differential biomarker for survival and treatment response in specific breast cancer subtypes. These studies add to the complex and diverse role of Ca(2+)-signalling in breast cancer progression and treatment.
authors.affiliation: The School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, 20 Cornwall St, Woolloongabba, Brisbane, QLD Australia.
authors.forename: Elena
authors.initials: E
authors.lastname: Pera
authors.affiliation: The School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, 20 Cornwall St, Woolloongabba, Brisbane, QLD Australia.|Mater Research Institute, The University of Queensland, Brisbane, QLD Australia.|Translational Research Institute, Brisbane, QLD Australia.
authors.forename: Elke
authors.initials: E
authors.lastname: Kaemmerer
authors.affiliation: The School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD Australia.
authors.forename: Michael J G
authors.initials: MJG
authors.lastname: Milevskiy
authors.affiliation: The School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, 20 Cornwall St, Woolloongabba, Brisbane, QLD Australia.
authors.forename: Kunsala T D S
authors.initials: KTDS
authors.lastname: Yapa
authors.affiliation: Translational Research Institute, Brisbane, QLD Australia.|Diamantina Institute, The University of Queensland, Brisbane, QLD Australia.
authors.forename: Jake S
authors.initials: JS
authors.lastname: O'Donnell
authors.affiliation: The School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD Australia.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Brown
authors.affiliation: Translational Research Institute, Brisbane, QLD Australia.|Diamantina Institute, The University of Queensland, Brisbane, QLD Australia.
authors.forename: Fiona
authors.initials: F
authors.lastname: Simpson
authors.affiliation: The School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, 20 Cornwall St, Woolloongabba, Brisbane, QLD Australia.
authors.forename: Amelia A
authors.initials: AA
authors.lastname: Peters
authors.affiliation: The School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, 20 Cornwall St, Woolloongabba, Brisbane, QLD Australia.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Roberts-Thomson
authors.affiliation: The School of Pharmacy, Pharmacy Australia Centre of Excellence, The University of Queensland, 20 Cornwall St, Woolloongabba, Brisbane, QLD Australia.|Mater Research Institute, The University of Queensland, Brisbane, QLD Australia.|Translational Research Institute, Brisbane, QLD Australia.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Monteith
keywords: Biomarker; Breast cancer; Calcium-signalling; Cav3.2 (CACNA1H); Therapeutic response; Trastuzumab-resistance