Inhibiting the glycerophosphodiesterase EDI3 in ER-HER2+ breast cancer cells resistant to HER2-targeted therapy reduces viability and tumour growth

Abstract

Background Intrinsic or acquired resistance to HER2-targeted therapy is often a problem when small molecule tyrosine kinase inhibitors or antibodies are used to treat patients with HER2 positive breast cancer. Therefore, the identification of new targets and therapies for this patient group is warranted. Activated choline metabolism, characterized by elevated levels of choline-containing compounds, has been previously reported in breast cancer. The glycerophosphodiesterase EDI3 (GPCPD1), which hydrolyses glycerophosphocholine to choline and glycerol-3-phosphate, directly influences choline and phospholipid metabolism, and has been linked to cancer-relevant phenotypes in vitro. While the importance of choline metabolism has been addressed in breast cancer, the role of EDI3 in this cancer type has not been explored. Methods EDI3 mRNA and protein expression in human breast cancer tissue were investigated using publicly-available Affymetrix gene expression microarray datasets (n = 540) and with immunohistochemistry on a tissue microarray (n = 265), respectively. A panel of breast cancer cell lines of different molecular subtypes were used to investigate expression and activity of EDI3 in vitro. To determine whether EDI3 expression is regulated by HER2 signalling, the effect of pharmacological inhibition and siRNA silencing of HER2, as well as the influence of inhibiting key components of signalling cascades downstream of HER2 were studied. Finally, the influence of silencing and pharmacologically inhibiting EDI3 on viability was investigated in vitro and on tumour growth in vivo. Results In the present study, we show that EDI3 expression is highest in ER-HER2 + human breast tumours, and both expression and activity were also highest in ER-HER2 + breast cancer cell lines. Silencing HER2 using siRNA, as well as inhibiting HER2 signalling with lapatinib decreased EDI3 expression. Pathways downstream of PI3K/Akt/mTOR and GSK3β, and transcription factors, including HIF1α, CREB and STAT3 were identified as relevant in regulating EDI3 expression. Silencing EDI3 preferentially decreased cell viability in the ER-HER2 + cells. Furthermore, silencing or pharmacologically inhibiting EDI3 using dipyridamole in ER-HER2 + cells resistant to HER2-targeted therapy decreased cell viability in vitro and tumour growth in vivo. Conclusions Our results indicate that EDI3 may be a potential novel therapeutic target in patients with HER2-targeted therapy-resistant ER-HER2 + breast cancer that should be further explored.

EDI3 knockdown in ER-HER2+ breast cancer cells reduces tumor burden and improves survival in two mouse models of experimental metastasis

“…However, acquired and inherent resistance has limited the efficacy of HER2-targeting drugs [ 5 ], supporting the need for novel treatment options for this patient subset. In our most recent work, we demonstrated that expression and enzymatic activity of the glycerophosphodiesterase EDI3 is highest in HER2+ breast cancer cells that are also estrogen receptor negative (ER-), and in agreement, higher EDI3 mRNA expression was also observed in human ER-HER2+ breast cancers in an analysis of publicly available Affymetrix gene expression microarray datasets [ 6 ]. Knocking down EDI3 with siRNA in the ER-HER2+ cell lines, SKBR3 and HCC1954 revealed a significant loss in cell viability [ 6 ].…”

“…In our most recent work, we demonstrated that expression and enzymatic activity of the glycerophosphodiesterase EDI3 is highest in HER2+ breast cancer cells that are also estrogen receptor negative (ER-), and in agreement, higher EDI3 mRNA expression was also observed in human ER-HER2+ breast cancers in an analysis of publicly available Affymetrix gene expression microarray datasets [ 6 ]. Knocking down EDI3 with siRNA in the ER-HER2+ cell lines, SKBR3 and HCC1954 revealed a significant loss in cell viability [ 6 ]. Furthermore, treating mice with the general phosphodiesterase inhibitor dipyridamole to pharmacologically inhibit EDI3 in vivo, resulted in a significant decrease in subcutaneous growth of tumors produced from HCC1954 cells.…”

“…Furthermore, treating mice with the general phosphodiesterase inhibitor dipyridamole to pharmacologically inhibit EDI3 in vivo, resulted in a significant decrease in subcutaneous growth of tumors produced from HCC1954 cells. These findings were validated using an in vivo mouse model that allowed us to inducibly silence EDI3 in HCC1954 cells by the addition of doxycycline [ 6 ], which altogether support EDI3 as a potential treatment target in ER-HER2+ breast cancer.…”

Zipper-Confined DNA Nanoframe for High-Efficient and High-Contrast Imaging of Heterogeneous Tumor Cell

“…7,8 Further, their intratumoral heterogeneity may become a key point in providing personalized diagnosis and treatment information. Although conventional bulk-volume sample testing methods (such as RT-qPCR 9 and microarrays 10,11 for nucleic acid substance; chemiluminescence immunoassay; 10 and western blot for proteins 12 ) have been widely used in clinical laboratories, these methods cannot provide temporal and spatial information about the substances being tested, thus overlooking intratumoral heterogeneity. Considering pinpointing nucleic acids and protein biomarkers in intact cells is indispensable for deciphering the mechanisms of disease development.…”

“…Homodimers and heterodimers of human epidermal growth factor receptor (HER) proteins tend to activate multiple signaling pathways of tumor progression. , In particular, the level of HER2 oligomerization potentially influences the therapeutic efficacy of first-line monoclonal antibody agents used for HER2-positive breast cancer. , Further, their intratumoral heterogeneity may become a key point in providing personalized diagnosis and treatment information. Although conventional bulk-volume sample testing methods (such as RT-qPCR and microarrays , for nucleic acid substance; chemiluminescence immunoassay; and western blot for proteins) have been widely used in clinical laboratories, these methods cannot provide temporal and spatial information about the substances being tested, thus overlooking intratumoral heterogeneity. Considering pinpointing nucleic acids and protein biomarkers in intact cells is indispensable for deciphering the mechanisms of disease development.…”