Gene targeting strategy for B-hHER3 MC38 cells. The exogenous promoter and human HER3 coding sequence was inserted to replace part of murine exon 2 and all of exons 3-7. The insertion disrupts the endogenous murine HER3 gene, resulting in a non-functional transcript.

HER3 expression analysis in B-hHER3 MC38 cells by flow cytometry. Single cell suspensions from wild-type MC38 and B-hHER3 MC38 cultures were stained with species-specific anti-HER3 antibody. Human HER3 was detected on the surface of B-hHER3 MC38 cells but not wild-type MC38 cells. The 2-G07 clone of B-hHER3 MC38 cells was used for in vivo tumor growth assays.

Subcutaneous homograft tumor growth of B-hHER3 MC38 cells. B-hHER3 MC38 cells (5x10⁶) and wild-type MC38 cells (5x10⁵) were subcutaneously implanted into C57BL/6 mice (female, 7-8-week-old, n=6). Tumor volume and body weight were measured twice a week. (A) Average tumor volume ± SEM. (B)  Body weight (Mean ± SEM). Volume was expressed in mm³ using the formula: V=0.5 X long diameter X short diameter². As shown in panel A, B-hHER3 MC38 cells were able to form tumors in vivo and can be used for efficacy studies.

B-hHER3 MC38 cells were subcutaneously transplanted into C57BL/6 mice (n=6). At the end of the experiment, tumor cells were harvested and assessed for human HER3 expression by flow cytometry. As shown, human HER3 was highly expressed on the surface of tumor cells. Therefore, B-hHER3 MC38 cells can be used for in vivo efficacy studies of HER3 therapeutics.