Trastuzumab

Biological Activity

In vitro: Trastuzumab has been demonstrated to exert a variety of anti-tumor effects selectively in HER2-overexpressing tumor cells. Trastuzumab binds to the juxtamembrane domain of HER2 and upon receptor binding, the antibody downregulates the expression of HER2. Trastuzumab selectively blocks ligand-independent HER2-HER3 dimerization. In addition, trastuzumab binding to HER2 blocks proteolytic cleavage of the extracellular domain of HER2, resulting in diminished levels of the more active p95-HER2 form of HER2. As a result of these effects on the HER2 receptor, trastuzumab causes downregulation of PI3K pathway signaling and downstream mediators of cell cycle progression such as cyclin D1. Trastuzumab not only inhibits HER2 signaling pathways but also triggers immune-mediated responses against HER2-overexpressing cells. Trastuzumab binding engages Fc receptors on immune effector cells leading to antibody-dependent cellular cytotoxicity. Beyond these effects, trastuzumab has been shown to have antiangiogenic effects and to lower the proapoptotic threshold for chemotherapy.

In vivo: Trastuzumab is shown to be safe when administered chronically to a range of animals including primates. In experiments mimicking adjuvant therapy of submacroscopic disease in vivo (JIMT-1 cells inoculated s.c. in severe combined immunodeficiency mice), trastuzumab is able to inhibit the outgrowth of macroscopically detectable xenograft tumors for up to 5-7 weeks. Trastuzumab has a remarkable antitumor effect and is currently used worldwide for the treatment of breast cancer. In in vivo models, trastuzumab decreases the microvessel density of breast cancer xenografts. It is well documented that trastuzumab acts directly in cancer cell signaling, as well as indirectly via the immune system.

Product Citations

• 

  Anal Chem. 2023 Sep 19;95(37):14094-14100.

  Amplification-Free Ratiometric Electrochemical Aptasensor for Point-of-Care Detection of Therapeutic Monoclonal Antibodies
  Trastuzumab purchased from AbMole

• 

  NPJ Breast Cancer. 2022 Jan;8(1):1.

  Effects of neoadjuvant trastuzumab, pertuzumab and palbociclib on Ki67 in HER2 and ER-positive breast cancer
  Trastuzumab purchased from AbMole

Protocol (for reference only)

Cell Experiment
Cell lines	JIMT-1, SKBR-3, and BT-474 cells
Preparation method	Exponentially growing cells are harvested and plated in single wells of a 96-well flat-bottomed tissue culture plate at defined densities, ranging from 4,500–8,000 cells per well depending on the cell line. After overnight culture, the regular medium is exchanged to medium containing 0, 1, 10, or 100 μg/mL trastuzumab or trastuzumab-F(ab′)2. Cell viability is tested after 72 h of treatment. Fluorescence is detected at an excitation of 544 nm, and emission is detected at 590 nm.
Concentrations	0, 1, 10, or 100 μg/mL
Incubation time	72 h

Animal Experiment
Animal models	SCID C.B-17 scid/scid and nu/nmri nude mouse
Formulation	saline
Dosages	5 μg/g
Administration	i.p.

Chemical Information

Molecular Weight	145529.41
Formula	C6470H10012N1726O2013S42
CAS Number	180288-69-1
Storage	Store at -20°C or -70°C. Avoid multiple freeze-thaws.

Conversion of different model animals based on BSA (PMID: 27057123)

Species	Mouse	Rat	Rabbit	Guinea pig	Hamster	Dog
Weight (kg)	0.02	0.15	1.8	0.4	0.08	10
Body Surface Area (m2)	0.007	0.025	0.15	0.05	0.02	0.5
Km factor	3	6	12	8	5	20

Animal A (mg/kg) = Animal B (mg/kg) multiplied by	Animal B Km
	Animal A Km

For example, to modify the dose of Compound A used for a mouse (20 mg/kg) to a dose based on the BSA for a rat, multiply 20 mg/kg by the K_m factor for a mouse and then divide by the K_m factor for a rat. This calculation results in a rat equivalent dose for Compound A of 10 mg/kg.

References

[1] Okita R, et al. Oncol Rep. Lapatinib enhances trastuzumab-mediated antibody-dependent cellular cytotoxicity via upregulation of HER2 in malignant mesothelioma cells.

[2] Han X, et al. Oncotarget. Tunicamycin enhances the antitumor activity of trastuzumab on breast cancer in vitro and in vivo.

[3] Hiroshima Y, et al. PLoS One. Tumor-Targeting Salmonella typhimurium A1-R in Combination with Trastuzumab Eradicates HER-2-Positive Cervical Cancer Cells in Pat ient-Derived Mouse Models.

[4] Nahta R, et al. Oncogene. Trastuzumab: triumphs and tribulations.