Sains Malaysiana 51(3)(2022): 859-864

http://doi.org/10.17576/jsm-2022-5103-19

Cytoplasmic and Nuclear HER4 Expression in HER2 Negative Breast Cancer Cell Lines

(Sitoplasma dan Pengekspresan Nuklear HER4 pada Titisan Sel Kanser Payudara HER2 Negatif)

SITI NORASIKIN MOHD NAFI^* & NURSYAZANA AQILAH ALI

Department of Pathology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kota Bharu, Kelantan, Malaysia

Received: 14 July 2020/Accepted: 12 August 2021

Abstract

HER4 cleavage and its subcellular localisations have been previously proven to mediate anti-HER2 resistance. The description of the HER4 subcellular localisations in HER2 negative breast cancer, on the other hand, is incomplete. The objective of this study was to determine the cytoplasmic and nuclear expression of HER4 in HER2 negative breast cancer cell lines in order to gain a better understanding of the key features of HER4 signalling in the context of anti-HER2 resistance. MCF-7 and MDA-MB-231 cells were cultured for 48 h at 37 °C and 5% CO₂ in fresh DMEM medium with 10% foetal bovine serum and 1% penicillin-streptomycin. The western blot analysis for HER4 protein was done on cytoplasmic and nuclear extracts that had been obtained previously using the NE-PER Nuclear and Cytoplasmic Extraction Kit. Cytoplasmic and nuclear HER4 proteins were expressed in a variety of sizes, including 120 kDa, 55 kDa, 50 kDa, and 43 kDa. MCF-7 cells expressed significantly more cytoplasmic HER4_120kDa than MDA-MB-231 cells. MCF-7 exhibited a single nuclear HER4 variant with a molecular weight of 50 kDa, whereas MDA-MB-231 expressed two nuclear HER4 variants with molecular weights of 50 kDa and 43 kDa. In comparison to MDA-MB-231 cells, MCF-7 cells exhibit higher level of cytoplasmic HER4_120kDa with positive nuclear HER4_50kDa expression. Due to the presence of ER and PR in MCF-7, it is important to investigate if the interaction of these HER4 variants with ER and PR confers resistance to anti-HER2 treatment on breast cancer. Meanwhile, results from MDA-MB-231 cells indicate that nuclear HER4 contributes to the development of TNBC.  

Keywords: Breast cancer; cytoplasmic HER4; HER2 negative; nuclear HER4

Abstrak

Pembelahan HER4 dan pensetempatan subselnya telah dibuktikan mempengaruhi kerintangan anti-HER2. Namun, penerangan mengenai pensetempatan subsel HER4 dalam barah payudara negatif HER2 masih tidak lengkap. Tujuan kajian ini adalah untuk menentukan pengekspresan sitoplasma dan nuklear HER4 dalam barisan sel barah payudara HER2 negatif untuk mendapatkan pemahaman yang lebih baik mengenai ciri utama isyarat HER4 dalam konteks ketahanan anti-HER2. Sel MCF-7 dan MDA-MB-231 dikultur selama 48 jam pada suhu 37 °C dan 5% CO₂ dalam media DMEM segar dengan 10% serum anak lembu dan 1% penisilin-streptomisin. Analisis pemblotan western untuk protein HER4 dilakukan pada ekstrak sitoplasma dan nuklear yang telah diperoleh sebelumnya menggunakan Kit Ekstraksi Nuklear NE-PER dan Sitoplasma. Protein sitoplasma dan nuklear HER4 diekspreskan dalam pelbagai ukuran, termasuk 120 kDa, 55 kDa, 50 kDa dan 43 kDa. Sel-sel MCF-7 mengekspreskan lebih banyak sitoplasma HER4_120kDa daripada sel MDA-MB-231. MCF-7 mempamerkan varian HER4 nuklear tunggal dengan berat molekul 50 kDa, sedangkan MDA-MB-231 menyatakan dua varian HER4 nuklear dengan berat molekul 50 kDa dan 43 kDa. Dibandingkan dengan sel MDA-MB-231, sel MCF-7 menunjukkan tahap sitoplasma HER4_120kDa yang lebih tinggi dengan mengekspreskan HER4_50kDa nuklear yang positif. Oleh kerana kehadiran ER dan PR dalam MCF-7, penting untuk mengkaji apakah interaksi varian HER4 ini dengan ER dan PR dalam menyebabkan kerintangan terhadap rawatan anti-HER2 pada barah payudara. Sementara itu, keputusan pada kajian sel-sel MDA-MB-231 menunjukkan bahawa HER4 nuklear menyumbang kepada perkembangan TNBC.

Kata kunci: HER4 nuklear; HER4 sitoplasma; kanser payudara; negatif HER2

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^*Corresponding author; email: snmn@usm.my