Synergism from combined immunologic and pharmacologic inhibition of HER2 in vivo

Area of Science:

• Oncology
• Immunology
• Biotechnology

Background:

• Trastuzumab and lapatinib improve outcomes for HER2-overexpressing breast cancer but resistance develops.
• Persistent HER2 overexpression in metastatic cancers necessitates alternative therapeutic strategies.

Purpose of the Study:

• To evaluate a recombinant adenoviral vector expressing a kinase-inactive HER2 (Ad-HER2-ki) as a cancer vaccine.
• To assess the efficacy of vaccine-induced anti-HER2 antibodies alone and in combination with lapatinib.
• To investigate the potential of this approach for treating trastuzumab- and lapatinib-refractory HER2-positive breast cancer.

Main Methods:

• Development of Ad-HER2-ki recombinant adenoviral vector cancer vaccine.
• Analysis of vaccine-induced polyclonal HER2-specific antiserum for receptor internalization and signaling effects.
• In vitro and in vivo studies evaluating the combination of Ad-HER2-ki vaccine and lapatinib.
• Assessment of HER2 signaling pathways (pERK, pAKT) and survivin expression.

Main Results:

• Ad-HER2-ki vaccine induced potent T cell and antibody responses in mice.
• Vaccine-induced antibodies effectively mediated HER2 receptor internalization and degradation, surpassing trastuzumab.
• Combination therapy significantly inhibited HER2 signaling, reduced breast tumor cell proliferation, and decreased pERK and pAKT levels.
• The combination therapy also inhibited survivin, a known resistance mechanism to lapatinib, and demonstrated superior antitumor efficacy in vivo.

Conclusions:

• The Ad-HER2-ki cancer vaccine effectively elicits anti-HER2 immune responses.
• Combining the HER2 vaccine with lapatinib demonstrates synergistic effects, enhancing tumor inhibition and overcoming resistance mechanisms.
• This combined therapeutic strategy holds significant promise for treating HER2-overexpressing breast cancer, including refractory cases, and warrants clinical trials.