HER-2 pulsed DC1(H. Lee Moffitt Cancer Center and Research Institute)

Patients with estrogen-independent (ER(neg)) human epidermal growth factor receptor-2 (HER-2)-positive ductal carcinoma in situ (DCIS) treated with lumpectomy alone or lumpectomy and radiation are at increased risk of developing subsequent breast cancer events.

Thirty-eight patients with HER-2 expressing DCIS received a HER-2 pulsed autologous dendritic cell (DC1) vaccine administered over 4-6 weeks before surgical resection. HER-2 and estrogen receptor (ER) expression were determined by immunohistochemistry. In 35 patients, CD4(pos) T-cell sensitization to HER-2 peptides was identified by ELISPOT. In 19 patients, CD8(pos) T-cell responses were identified by ELISA. Clinical and immune responses postvaccination were compared between intermediate-expressing HER-2 (2+) and high-expressing HER-2 (3+) patients, as well as ER(neg) and estrogen-dependent (ER(pos)) patients.

There was no significant difference in immune response after HER-2 vaccination in patients with HER-2 (2+) and (3+) tumors or ER(neg) and ER(pos) tumors. Complete tumor regression rates were similar in patients with HER-2 (2+) and (3+) DCIS. Overall, clinical response rates were similar in patients with ER(neg) and ER(pos) DCIS, but complete tumor regression was significantly more common in patients with ER(neg) DCIS.

Despite equivalent immune responses after vaccination in patients with HER-2 (2+), HER-2 (3+), ER(neg) and ER(pos) DCIS, HER-2 pulsed DC1 induces more complete responses in patients with ER(neg) DCIS. These data provide a rationale for developing vaccinations to reduce recurrence in patients with ER(neg) DCIS for whom there are currently limited adjuvant options.

The present study uses an in vivo murine tumor model expressing the human HER-2/neu antigen to evaluate the potential vaccine using dendritic cells (DCs) infected with adenovirus AdVHER-2. We first investigated whether infected DCs (DC(HER-2)) engineered to express HER-2/neu could induce HER-2/neu-specific immune responses. Our data showed that (i) AdVHER2-infected DC(HER-2) expressed HER-2/neu by Western blot and flow cytometric analysis, and (ii) vaccination of mice with DC(HER-2) induced HER-2/neu-specific cytotoxic T-lymphocyte (CTL) responses, but protected only 25% of vaccinated mice from challenge of 3 x 10(5) MCA26/HER-2 tumor cells. Further, to enhance the efficacy of DC(HER-2) vaccine, we coinfected DCs with both AdVHER-2 and AdVTNF-alpha. The infected DCs (DC(HER-2/TNF-alpha)) displayed the expression of both HER-2/neu and TNF-alpha by flow cytometric and ELISA analysis. We next investigated whether DC(HER-2/TNF-alpha) could induce stronger HER-2/neu-specific immune responses. We found that DC(HER-2/TNF-alpha) displayed up-regulation of immunologically important CD40, CD86, and ICAM-I molecules compared with DC(HER-2), indicating that the former ones are more mature forms of DCs. Vaccination of DC(HER-2/TNF-alpha) induced stronger allogeneic T-cell proliferation and 36% enhanced HER-2/neu-specific T-cell responses in vitro than DC(HER-2) cells. More importantly, it stimulated the significant anti-HER-2/neu immunity in vivo, which protected 8/8 mice from challenge of 3 x 10(5) MCA26/HER-2 tumor cells. Therefore, DCs genetically engineered to express both the tumor antigen and cytokines such as TNF-alpha as an immunoadjuvant are likely to represent a new direction in DC vaccine of cancer.