Synergism from combined immunologic and pharmacologic inhibition of HER2 in vivo

Abstract

The monoclonal antibody trastuzumab and the EGFR/HER2 tyrosine kinase inhibitor lapatinib improve the clinical outcome of patients with HER2-overexpressing breast cancer. However, the majority of metastatic cancers will eventually progress, suggesting the need for other therapies. Because HER2 overexpression persists, we hypothesized that the anti-HER2 immune response induced by cancer vaccines would be an effective strategy for treating trastuzumab-and lapatinib-refractory tumors. Furthermore, we hypothesized that the antibody response could synergize with lapatinib to enhance tumor inhibition. We developed a recombinant adenoviral vector expressing a kinase-inactive HER2 (Ad-HER2-ki) to use as a cancer vaccine. Vaccine-induced polyclonal HER2-specific antiserum was analyzed for receptor internalization and signaling effects alone and in combination with lapatinib. Ad-HER2-ki vaccine-induced potent T cell and antibody responses in mice and the vaccineinduced polyclonal HER2-specific antiserum mediated receptor internalization and degradation much more effectively than trastuzumab. Our in vitro studies demonstrated that HER2 vaccine-induced antibodies effectively caused a decrease in HER2 expression, but when combined with lapatinib caused significant inhibition of HER2 signaling, decreased pERK and pAKT levels and reduced breast tumor cell proliferation. In addition, a known mechanism of resistance to lapatinib, induction of survivin, was inhibited. The combination of Ad-HER2-ki plus lapatinib also showed superior antitumor efficacy in vivo. Based on these results, we feel clinical studies using this approach to target HER2-overexpressing breast cancer, including trastuzumab-and lapatinib-resistant tumors is warranted.The human epidermal growth factor receptor (HER) 2, overexpressed in 20-30% of breast cancers, is associated with more aggressive tumors and inferior overall survival.1 Combinations of the anti-HER2 antibody trastuzumab and chemotherapy lengthen survival in metastatic HER2-overexpressing breast cancer.2 However, progressive disease typically occurs within 1 yr. Lapatinib, a potent reversible inhibitor of HER2 and EGFR tyrosine kinases, 3 in conjunction with chemotherapy, enhances time to progression in these patients. 4 Unfortunately, responses to lapatinib are generally short lived and progression remains a significant clinical problem.Intriguingly, the overexpression of HER2 persists in trastuzumab and lapatinib-refractory tumors, 5,6 and thus, targeting HER2 with T cells and antibodies induced by cancer vaccines is a potentially effective strategy. More than a dozen phases I and II studies of cancer vaccines have been conducted in breast cancer patients. 7 These vaccines have included proteins, peptides, modified tumor cells and dendritic cells loaded with breast tumor antigens. In these studies,

Type III TGF-β receptor downregulation generates an immunotolerant tumor microenvironment

“…Previously described 4T1-NEO and 4T1-TGFBR3 murine mammary carcinoma cell lines (H-2 d ) (22) were maintained in DMEM, 10% FBS, and 200 μg/ml G418. The 4T1-HER2 (H-2 d ) cell line was cultured as previously described (37). The 66CL4 murine mammary carcinoma cell line (H-2 d ) (gift from F. Miller, Wayne State University School of Medicine, Detroit, Michigan, USA) was cultured in DMEM, nonessential amino acids, l-glutamine, and 10% FBS (52).…”

“…For TGF-β inhibitor studies, 4T1-HER2 tumor cells were implanted into the right mammary fat pad of syngeneic female BALB/c mice (7 weeks of age), and growth was allowed to progress until tumors became palpable on day 11. Mice were either initiated on chow formulated with the type I TGF-β serine/threonine kinase inhibitor SM16 (Biogen Idec) or on regular drug-free chow (Research Diets) for 3 days, before tumor-bearing mice were vaccinated and boosted 5 days later via intradermal fat pad injection either with AdHER2ki or with AdLacZ as negative control (2.6 × 10 10 viral particles/mouse) (37,38,40). Tumor growth was monitored by caliper, and spleens were removed on day 30 after implantation for further ELISPOT analysis.…”

Immune consequences of kinase inhibitors in development, undergoing clinical trials and in current use in melanoma treatment

“…In an animal model for HER2-positive breast cancer, the combination of lapatinib with doxorubicin resulted in enhanced tumor infiltration by IFN-g-secreting T cells than after single treatments, suggesting that lapatinib promotes a proimmunogenic response [149]. Lapatinib administered with a HER2-vaccine did not impact the immune response to immunization in both mice and HER2-overexpressing breast cancer in humans [150,151], although the presence of Tregs was not assessed in all studies [152].…”

“…While it will be too early to declare these patients cured, there will be an established perception that these combinations are effectively converting a once fatal disease into one that can be controlled, possibly indefinitely. Dual PI3K/mTOR BEZ235 [171] PF-0469150 EGFR Lapatinib [149][150][151] Erlotinib [155,157] PKC AEB071 [204,212,213] Immune consequences of KIs Review informahealthcare.com Combination immunotherapy will be well on the way to being established as a mainstream effective standard of care.…”

Anti-HER2 vaccines: new prospects for breast cancer therapy

“…Very recently, Morse et al [114] demonstrated in vivo that the combination of a recombinant adenoviral vector that expresses kinase-inactive HER2 (Ad-HER2-ki) and lapatinib (an oral dual receptor tyrosine kinase inhibitor that targets both HER1 and HER2 receptors) caused significant inhibition of HER2 signaling in vitro and higher anti-tumor efficacy in vivo in a mouse model than the vaccine alone.…”