Breast cancer is a highly heterogeneous malignant tumor, whose biological behavior is closely related to her-2 status. Her-2 subtype breast cancer often presents with disease relapse and metastasis, and the survival rate is low. In recent years, targeted drugs therapies have improved overall survival for HER-2 subtype breast cancer patients [18]. Despite this standardized initial therapy, with the development primary and secondary resistance to targeted drugs, some patients could rapidly developed disease progression [19]. Thus, further studies will be needed to explore the pathogenesis and search new therapeutic targets.
In this study, we identified 503 DEGs in the GSE29431 using LIMMA package. Among 503 DEGs, 96 genes were up-regulated and 407 genes were down-regulated The GO enrichment analysis showed that DEGs were mainly related to regulation of lipid metabolic process (BP term), while the KEGG pathway enrichment analysis showed that DEGs were mainly enriched PPAR signaling pathway and PI3K-Akt signaling pathway. Using STRING database and Cytoscape software, we constructed PPI network and identified 12 target genes (CCNB1, CENPF, NUSAP1, CEP55, PTTG1, TOP2A, MELK, AURKA, UBE2C, BUB1B, CENPF,, AURKA, UBE2C, BUB1B, KIF20A and RRM2). And the reliability of 12 target genes was further validated by UVALCAN database. Finally, using Kaplan-Meier plotter, we found that over-expression of key genes were associated with poor prognosis.
The lipid metabolism is closely associated with breast cancer[20,21]. It has been reported the use of statins reduced the chance of recurrence. in breast cancer [22]. Activated glutamine metabolism in HER-2 positive breast cancer had clinical implication as a potential therapeutic target [23]. PPAR pathway plays a major role in regulating cancer cell proliferation. Ham et al [24] found that the PPAR with c-Myc governed the tumorigenicity of breast cancer. However, it is unclear whether PPAR signaling pathway is involved in targeted drug resistance. Further studies are needed to validate this. The PI3K/AKt pathway, as an important intracellular signaling path, participated in the development of breast cancer [25]. Studies have suggested that inhibition of PI3K/AKT/mTOR pathway can improve resistance to anti-HER2 therapies. According to BOLERO-3 trial [26], the addition of everolimus, a mTOR inhibitor, significantly prolonged PFS in trastuzumab resistance in HER2‐overexpressing breast cancer (7.0 vs 5.8 months, p = 0.0067).
NUSAP1 is a microtubule-associated protein, which take a important part in the spindle assembly and cell proliferation. NUSAP1 has been shown to be closely related to the development of breast cancer and renal cell carcinoma [27,28]. Knockdown of NUSAP1 inhibited the the migration, proliferation and invasion of IBC cells [29]. Pituitary tumor-transforming gene 1 (PTTG1) serves as a proto-oncogene and regulates sister chromatid separation [30]. Additionally, PTTG1 overexpression, commonly observed in many malignant tumor, promoted the invasive ability of tumor cells [31-32]. According to the expression pattern of PTTG1 in primary and metastatic breast cancer, it was expexcted to be an important molecular target in breast cancer treatment [33]. Studies showed silencing PTTG1 gene was an effective method for the treatment of liver cancer [34]. CEP55 is a key regulator of cytokinesis, and was associated with genomic instability [35]. Notably, the proliferative potential and invasive ability of the breast cancer cells were markedly reduced when CEP55 was down-regulated [36]. TOP2A gene is located on human chromosome 17q21, and is closely related to invasive and proliferative potential. Clinical studies have showed that TOP2A played a predictive role for anthracycline-based chemotherapy [37]. CCNB1, known as cyclin B1, is a highly conserved cyclin. Testing cyclin B1 in patients treated with T-DM1 was benifical to identify early the patients more likely to benefit from this drug [38]. CENPF is a cell cycle-regulated protein associated with kinetochores, and is overexpressed in breast cancer, hepatocellular carcinoma and other tumors[39-40]. CENPF was reported to be a novel target protein contributing to the anti-tumour effects of zoledronic acid [41].
MELK is a serine/threonine kinase in the snf1/AMPK family, and is associated with undifferentiated phenotype, poor prognosis, chemoresistance, and Radioresistance [42]. Many studies showed MELK was a significantly therapeutic target for breast cancer [43]. AURKA, a human Aurora kinase, can promote cell cycle and suppress cell apoptosis. By stimulating the PI3K/AKT/mTOR pathway, Overexpressed AURKA activated the development of chemotherapeutic resistance [44,45]. UBE2C, as a member of the ubiquitin-conjugating enzyme family (E2), was associated to the progression of cancers [46]. Mo et al [47] reported UBE2C expression was positively correlated with HER2 expression (P<0.05). Additionally, the suppression of UBE2C could inhibit growth of BRCA cells and sensitized breast cancer cells to doxorubicin [48]. BUB1 mitotic checkpoint serine/threonine kinase B (BUB1B) encodes a kinase participating in the spindle checkpoint, and is in correlation with distant metastasis and progression of breast carcinoma [49]. Kinesins (also known as KIFs) are a superfamily of molecular motors engaged in mitosis and migration. Khongkow et al identified KIF20A was involved in paclitaxel action and resistance [50]. Ribonucleotide reductase M2 subunit (RRM2), a rate-limiting enzyme for DNA synthesis and repair, was associated with cell proliferation, invasiveness and migration [51]. Previous study suggested that targeting RRM2 may be a novel strategy for breast cancer treatment. Small molecular antagonist of RRM2 gene significantly reduced tamoxifen-resistant cell proliferation and decreased tumor growth [52]. Suppression of RRM2 synthesis could enhance the chemosensitivity to adriamycin [53].
In present study, using bioinformatics analysis, we identified 12 potential targeted genes in HER-2 positive breast cancer, and these findings provided new targets for diagnosis and treatment. However, animal experiments and population-based studies are necessary to confirm the results in this study.