In Pancreatic Carcinoma, Dual EGFR/HER2 Targeting with Cetuximab/Trastuzumab Is More Effective than Treatment with Trastuzumab/Erlotinib or Lapatinib Alone: Implication of Receptors' Down-regulation and Dimers' Disruption

Abstract

We previously demonstrated the synergistic therapeutic effect of the cetuximab (anti-epidermal growth factor receptor [EGFR] monoclonal antibody, mAb)-trastuzumab (anti-HER2 mAb) combination (2mAbs therapy) in HER2(low) human pancreatic carcinoma xenografts. Here, we compared the 2mAbs therapy, the erlotinib (EGFR tyrosine kinase inhibitor [TKI])-trastuzumab combination and lapatinib alone (dual HER2/EGFR TKI) and explored their possible mechanisms of action. The effects on tumor growth and animal survival of the three therapies were assessed in nude mice xenografted with the human pancreatic carcinoma cell lines Capan-1 and BxPC-3. After therapy, EGFR and HER2 expression and AKT phosphorylation in tumor cells were analyzed by Western blot analysis. EGFR/HER2 heterodimerization was quantified in BxPC-3 cells by time-resolved FRET. In K-ras-mutated Capan-1 xenografts, the 2mAbs therapy gave significantly higher inhibition of tumor growth than the erlotinib/trastuzumab combination, whereas in BxPC-3 (wild-type K-ras) xenografts, the erlotinib/trastuzumab combination showed similar growth inhibition but fewer tumor-free mice. Lapatinib showed no antitumor effect in both types of xenografts. The efficacy of the 2mAbs therapy was partly Fc-independent because F(ab')(2) fragments of the two mAbs significantly inhibited BxPC-3 growth, although with a time-limited therapeutic effect. The 2mAbs therapy was associated with a reduction of EGFR and HER2 expression and AKT phosphorylation. BxPC-3 cells preincubated with the two mAbs showed 50% less EGFR/HER2 heterodimers than controls. In pancreatic carcinoma xenografts, the 2mAbs therapy is more effective than treatments involving dual EGFR/HER2 TKIs. The mechanism of action may involve decreased AKT phosphorylation and/or disruption of EGFR/HER2 heterodimerization.

Inhibition of pancreatic carcinoma by homo- and heterocombinations of antibodies against EGF-receptor and its kin HER2/ErbB-2

“…Although single mAbs induced partial disappearance of their direct targets, the combination of a mAb to EGFR and another to HER2 almost completely eliminated both receptors. Notably, a similar observation was made using a different set of mAbs (25), and another report documented the ability of an anti-HER2 antibody to increase EGFR endocytosis, probably by dissociating preformed EGFR-HER2 complexes (34). Hence, it is conceivable that heterocombinations of mAbs interfere with the previously reported inclination of EGFR-HER2 heterodimers to avoid the degradative fate by enhancing receptor recycling (35,36).…”

“…The other strategy combined two antibodies, one to EGFR and the other to HER2, in similarity to reports by Azria, Pelegrin, and coworkers, who combined two antibodies (24) and also added a third agent, namely a tyrosine kinase inhibitor (25). Here, we compare the two types of antibody combinations and also highlight potential mechanisms of the synergy observed in animals bearing human PDAC xenografts.…”

“…Another reason to suspect additional, non-ADCC or complement-mediated mechanisms derives from the observed partial effect of trastuzumab in mice lacking certain fragment crystalizable (Fc) receptor molecules (10). In the same vein, bivalent fragments of anti-EGFR and anti-HER2 antibodies retained synergy, despite absence of the Fc tails (25).…”

Pan-HER, an Antibody Mixture Simultaneously Targeting EGFR, HER2, and HER3, Effectively Overcomes Tumor Heterogeneity and Plasticity

“…5B). Pan-HER displays superior in vivo activity due to synergistic effects of targeting EGFR, HER2, and HER3 To further address the specific contribution of the individual target specificities in the Pan-HER antibody mixture and to assess potential synergies, single-, dual-, and triple-receptor targeting was tested in two xenograft models, BxPC3 and Calu-3, previously used to demonstrate synergistic effects of combined HER family receptor targeting (35)(36)(37)(38).…”

Cancer Immunotherapy: More Is (Much) Better

“…Hence, it would be worthwhile testing less complex mixtures of two to four mAbs, which are expected to be less toxic and, presumably, as effective as Pan-HER. This option has been supported by pancreatic cancer studies that utilized mixtures comprising anti-HER2 and anti-EGFR antibodies (11,12). A similar option is offered by recombinant bispecific antibodies able to simultaneously bind two HER proteins.…”