The voltage gated Ca2+-channel Cav3.2 and therapeutic responses in breast cancer

Abstract

BackgroundUnderstanding the cause of therapeutic resistance and identifying new biomarkers in breast cancer to predict therapeutic responses will help optimise patient care. Calcium (Ca2+)-signalling is important in a variety of processes associated with tumour progression, including breast cancer cell migration and proliferation. Ca2+-signalling is also linked to the acquisition of multidrug resistance. This study aimed to assess the expression level of proteins involved in Ca2+-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.MethodsExpression levels of a panel of Ca2+-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).ResultsIncreased 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.ConclusionOur 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 Ca2+-signalling in breast cancer progression and treatment.Electronic supplementary materialThe online version of this article (doi:10.1186/s12935-016-0299-0) contains supplementary material, which is available to authorized users.

Immunohistochemical analysis of T-type calcium channels in acquired melanocytic naevi and melanoma

“…In fact, Pera et al . have recently shown that high levels of Cav3.2 (measured by quantitative RT‐PCR) were associated with poor outcome in patients with oestrogen receptor‐positive breast cancers, whereas in patients with HER2‐positive breast cancers, high Cav3.2 levels were associated with better OS after chemotherapy . Although Cav3.1 or Cav3.2 Hs in primary tumours did not show an impact on the prognosis (OS and DFS) of our patients ( n = 39; data not shown), we decided to perform a bioinformatics analysis from a larger number of patients.…”

Ca2+ mediates extracellular vesicle biogenesis through alternate pathways in malignancy

“…In breast cancer cells, the calcium channel TRPC5 is important in MDR via extracellular vesicles [45]. For this reason, the therapeutic targeting of calcium signalling presents clinical opportunities [40,46]. Despite the known relationship between elevated intracellular calcium and plasma membrane vesiculation, the exact pathway(s) and channels involved in biogenesis remain to be fully defined.…”

Amplification of a calcium channel subunit CACNG4 increases breast cancer metastasis

“…It was also ranked as the 10th most overexpressed gene out of 45 other genes up-regulated by androgens in human prostate cancer xenografts in mice [23]. In breast cancer, only T-type VGCCs have been found to be overexpressed in the HER2-positive SKBR3 cell line that acquired resistance to trastuzumab, as well as in luminal versus basal breast cancers [5]. They have also been associated with an increase in cell proliferation of the luminal breast cancer cell line MCF7 compared to non-malignant MCF10A breast epithelial cells, which could be curbed with calcium channel blockers [24,25].…”