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The Epidermal Growth Factor Receptor (EGFR) serves as the receptor for the Epidermal Growth Factor (EGF), mediating cellular proliferation and signal transduction. EGFR belongs to the HER receptor family, a group comprising four related proteins: EGFR (HER1/ErbB1), ERBB2 (HER2), ERBB3 (HER3), and ERBB4 (HER4). These receptors are classified as receptor tyrosine kinases; they are situated on the cell membrane surface and are activated through binding with specific ligands. Notably, ERBB2 is the sole member of the ErbB (HER) family for which no known ligand has been identified; however, it is capable of binding with other family members to form dimeric receptor structures.

HER receptors are activated through binding with various ligands, including EGF, TGFA, heparin-binding EGF-like growth factor (HB-EGF), amphiregulin, beta-cellulin, and epiregulin. Upon ligand binding to the extracellular domain of the receptor, the receptor forms a functionally active dimer—either a homodimer (e.g., EGFR-EGFR) or a heterodimer (e.g., EGFR-HER2, EGFR-HER3, or EGFR-HER4). This dimerization event triggers the activation of the receptor's tyrosine kinase domain, subsequently leading to the autophosphorylation of multiple tyrosine residues on the receptor. Consequently, this process recruits a series of adaptor proteins (such as SHC and GRB2) and initiates a cascade of intracellular signaling pathways that influence gene transcription. Ultimately, this leads to the proliferation of cancer cells, a reduction in apoptosis, increased cellular invasion and metastasis, and the stimulation of tumor-induced angiogenesis.

The EGFR & ERBB3 Dimerization CHO Reporter Gene Drug Target Model effectively simulates the *in vivo* signal transduction processes involving EGFR and ERBB3; the underlying principle is illustrated in the figure below.

Figure 1. Schematic Diagram of the CHO-K1 Human EGFR&ERBB3 Dimerization Cell Model

Figure 2. Recombinant EGFR&ERBB3 Dimerization CHO stably expressing EGFR&ERBB3.

Figure 3. Dose Response of Ligands in EGFR&ERRB3 Dimerization CHO Cell( C3).

Figure 4. Inhibition of Recombinant Human NRG-β1 induced EGFR&ERBB3 Dimerization by EGFR or ERBB3 Abs in EGFR&ERBB3 Dimerization CHO Cell(C3).

Figure 5. Inhibition of Recombinant Human NRG-β2 induced EGFR&ERBB3 Dimerization by EGFR or ERBB3 Abs in EGFR&ERBB3 Dimerization CHO Cell ( C3).

Cell Resuscitation
1)Rapidly thaw the frozen cells in a 37 °C water bath for approximately 60 seconds. Once thawed (which may take slightly less or more than 60 seconds), immediately transfer the cell suspension from the cryovial into a 15 mL centrifuge tube containing 10 mL of pre-warmed  CHO-K1 Human EGFR&ERBB3 Dimerization Cell complete culture medium.
2)Centrifuge cells at 1000 rpm for 5 min to remove medium, then resuspend cells in 5 mL of pre-warmed complete medium.
3)Transfer the cell suspension into a T25 culture flask and incubate at 37 °C with 5% CO₂.
4)After approximately 24–36 hours, replace the medium or passage the cells to remove non-adherent dead cells.

Subculturing procedure
1)When the cell density reaches the appropriate confluency for passaging, wash the cells with PBS, then add 1 mL trypsin to detach the cells. When more than 80% of the cells detach upon gently tapping the culture flask, add complete culture medium to terminate digestion. Gently pipette to obtain a single-cell suspension, transfer to a 15 mL centrifuge tube, and centrifuge at 1000 rpm for 5 minutes.

2)Discard supernatant after centrifugation. Resuspend cells in fresh medium to a single-cell suspension and transfer to a new culture flask for continued growth.

Cell Freezing
After trypsinization and centrifugation of cells from each T75 flask or 10 cm culture dish, discard the supernatant. Add 2 mL of cryopreservation medium (90% FBS + 10% DMSO), gently resuspend thoroughly, and aliquot into two cryovials. Immediately place the cryovials into a controlled-rate freezing container (e.g., Nalgene 5100-0001), fill with isopropanol to the indicated level, and store at −80 °C. After 24 hours, transfer the cryovials to liquid nitrogen for long-term storage.