Neoadjuvant Vaccination Provides Superior Protection against Tumor Relapse following Surgery Compared with Adjuvant Vaccination Natalie Grinshtein, Byram Bridle, Yonghong Wan, and Jonathan L. Bramson Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada Abstract Tumors that recur following surgical resection of melanoma are typically metastatic and associated with poor prognosis. Using the murine B16F10 melanoma and a robust antimela- noma vaccine, we evaluated immunization as a tool to improve tumor-free survival following surgery. We investigat- ed the utility of vaccination in both neoadjuvant and adjuvant settings. Surprisingly, neoadjuvant vaccination was far supe- rior and provided f100% protection against tumor relapse. Neoadjuvant vaccination was associated with enhanced frequencies of tumor-specific T cells within the tumor and the tumor-draining lymph nodes following resection. We also observed increased infiltration of antigen-specific T cells into the area of surgery. This method should be amenable to any vaccine platform and can be readily extended to the clinic. [Cancer Res 2009;69(9):3979–85] Introduction Surgery is the leading treatment modality for melanoma and most solid tumors. More than 90% of primary melanomas can be cured by surgical resection if diagnosed early. However, resection alone is rarely curative for advanced tumors due to either local tumor recurrence or outgrowth of micrometastases. In that regard, patients with stage II melanoma are at high risk for recurrent disease and are reported to have only 40% to 60% chance of survival 5 years after the surgery (1). Cancer vaccines offer an appealing strategy to improve disease- free survival following surgical resection. Preclinical studies have shown that cancer vaccines can routinely confer protection in prophylactic settings, but the same vaccines usually exhibit only limited therapeutic efficacy (2, 3). We have observed that existing tumors can suppress immunity against tumor-associated antigens, limiting the activity of cancer vaccines (4). Furthermore, in patients with advanced-stage disease, tumor progression can occur within the window of time required for induction of an immune response following vaccination. Based on these data, it seems logical that cancer vaccines would be most useful as an adjuvant treatment in the setting of minimal residual disease. Alternatively, cancer vaccines could be employed in the neoadjuvant setting. Under these circumstances, surgical resection could be timed to coincide with the peak of the immune response. Indeed, such a strategy has been evaluated in the clinic (5, 6). These reports showed evidence of vaccine immunogenicity, but these studies were not sufficiently powered to make conclusion regarding efficacy. To date, however, the issue of whether neoadjuvant immunization provides an advantage over adjuvant immunization has not been addressed. Thus, the optimal vaccination schedule remains unknown. With regards to melanoma, a limited number of randomized clinical trials have tested the efficacy of adjuvant vaccination (7–9). All of those trials were halted early because vaccination did not affect improve either disease-free or overall survival. It was unclear from those studies whether the lack of clinical benefit was due to the strategy (adjuvant vaccination) or the vaccine. We have found that replication-defective adenovirus (rAd)-based cancer vaccines produce robust antitumor immunity. In particular, a rAd vector expressing human dopachrome tautomerase (AdhDCT) provided superior protection against the murine B16F10 melanoma compared with rAd vectors expressing other melanoma-associated antigens (10–13). 1 DCT (also called tyrosinase-related protein 2) is a promising candidate for the development of melanoma vaccines, as it is widely expressed in melanoma and is naturally recognized by melanoma-specific CTLs (14, 15). Despite the robust activity of AdhDCT in prophylactic models (10, 11), we have observed that vaccination with AdhDCT was ineffective even when the vaccine was administered as little as 1 day after seeding the tumor (4), suggesting that AdhDCT may only be useful in the setting of minimal tumor burden. Given the robust protective immunity provided by AdhDCT in prophylactic, but not therapeutic, settings, we reasoned that this vaccine would provide a stringent test for our hypothesis that immunization against tumor antigen(s) may improve disease-free survival following surgery. To this end, we investigated the effect of neoadjuvant and adjuvant immuniza- tion with AdhDCT on tumor relapse in the B16F10 melanoma model. Materials and Methods Mice. Six- to 8-week-old female C57BL/6 mice were obtained from Charles River Breeding Laboratories. All of our investigations have been approved by the McMaster Animal Research Ethics Board. rAd and immunizations. All rAd vectors employed in this study contain deletions of E1 and E3 regions (16). The expression cassettes were inserted into the E1 region under the control of the murine cytomegalovirus (CMV) promoter and the SV40 polyadenylation sequence. The rAd vectors were propagated using 293 cells and purified using CsCl gradient centrifugation as described previously (17). AdhDCT encodes the full-length human DCT (11). AdLCMV GP expresses the sequence corresponding to residues 33 to Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Requests for reprints: Jonathan L. Bramson, Department of Pathology and Molecular Medicine, McMaster University, Room MDCL-5025, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5. Phone: 905-525-9140; Fax: 905-522-6750; E-mail: bramsonj@mcmaster.ca. I2009 American Association for Cancer Research. doi:10.1158/0008-5472.CAN-08-3385 1 Unpublished data. www.aacrjournals.org 3979 CancerRes2009;69:(9).May1,2009 Research Article Research. on March 6, 2016. © 2009 American Association for Cancer cancerres.aacrjournals.org Downloaded from Published OnlineFirst April 21, 2009; DOI: 10.1158/0008-5472.CAN-08-3385