**4. Selection of a tumor antigen target**

136 Cancer Prevention – From Mechanisms to Translational Benefits

presented with low antigen levels of early disease or early recurrence [44]. In addition, patients with early stage breast cancer do not require aggressive adjuvant therapy. The immune response in vaccinated patients with early stage cancers will not be compromised by the limitations of these cytotoxic treatments, most importantly the long-term reductions in functioning B and T lymphocytes [45-47]. There has therefore been a shift in the field of immunotherapy towards the treatment of patients with minimal disease and the prevention

With the increasing use of screening mammography, DCIS, the pre-invasive form of breast cancer, has become the most frequently diagnosed breast malignancy. DCIS is a heterogeneous disease both in terms of nuclear grade and expression of cell-surface receptors. DCIS is the non-obligate precursor of invasive ductal carcinoma. Low-grade DCIS may develop into invasive cancer slowly or not all. In contrast, high-grade DCIS almost always develops into invasive disease and often requires more aggressive surgical and

Currently, in most clinical practices, DCIS lesions are examined for the over-expression of ER and PR. Interest in the correlation between the molecular biology of DCIS and its clinical aggressiveness has led to staining for other markers. The additional information about potential antigen targets on DCIS is useful to guide development of novel adjuvant vaccines against DCIS. Specifically, for the past 6 years we have routinely stained all of the tumors from our DCIS patients for the over-expression of HER-2. Other biologic markers that are may have prognostic significance include HER 1-4, Ki67, p21, bcl-2, p16 and COX-2, c-myc

Multiple recent studies have concentrated on determining molecular phenotypes for DCIS similar to those described for invasive breast cancer. In 2010 *Tamimi et al* published a large case series of DCIS and invasive breast tumors that were analyzed using tissue microarray and immunostaining for ER, PR, HER-2, CK 5/6 and EGFR. The authors concluded that the same 5 molecular phenotypes used to describe invasive cancer were all identified among the cases of DCIS. The prevalence of the lesions was not consistent between the DCIS and invasive tumors; the Luminal A phenotype was significantly more frequent among the invasive cancers and the Luminal B and HER-2 molecular phenotypes were more frequent in DCIS. The triple negative (Basal-like) phenotype is very uncommon in DCIS [50]. This is consistent with other studies that show a higher prevalence of HER-2 over expression in DCIS compared to invasive breast cancer [51-53]. Additional work has expanded the traditional molecular profiling to incorporate many more biomarkers that have been found to be biologically relevant to invasive breast cancer, including p53, bcl-2 and P-cadherin. Bcl-2 was found to be one of the most common genes to be up regulated in the welldifferentiated sample of DCIS [53] and has also been reported to be a predictor of good

DCIS is a particularly attractive vaccine target because the elimination of this disease prevents the subsequent development of invasive breast cancer. In addition, a novel neoadjuvant vaccine would be ideal to reduce size of these lesions prior to surgery. This could theoretically decrease the amount of breast tissue required to obtain clear margins

breast cancer formation.

adjuvant therapy [48].

and survivin [10, 13, 49].

prognosis in invasive breast cancers [54].

**3.1 Immunotherapy and ductal carcinoma in situ** 

The selection of an appropriate target tumor antigen is paramount to the success of any cancer vaccine. The ideal vaccine would stimulate a significant immune response without causing autoimmunity and without a detrimental side effect profile. One strategy to avoid autoimmunity and to enhance the specificity of the vaccine is to target tumor antigens that are overexpressed in cancer cells but have minimal expression in normal cells. As mentioned in a previous section, one challenge to targeting oncogenic molecules is that these tumor associated antigens are usually only weakly immunogenic and are therefore capable of evading the immune response, or the immune system can immunoedit the tumors leaving behind antigen negative tumor cells. Many of the breast cancer tumor antigens are also overexpressed in other cancers of epithelial cell origin (colon cancer and ovarian cancer). Previously targeted peptides in the experimental production of vaccines against breast cancer include Mucin (MUC)-1, Her-2, carcinoembryonic antigen (CEA), and survivin [56-58].

### **4.1 The EGF receptor family**

The epidermal growth factor receptor (EGFR) family is a group of four related transmembrane receptor tyrosine kinases that have been implicated in the development of a multiple solid malignancies and have subsequently been targeted in a variety of novel therapeutics [59]. The EGFR family consists of HER-1 (also known as ERBB1), HER-2 (ERBB2), HER-3 (ERBB3) and HER-4 (ERBB4). These receptors bind 13 different ligands and form a number of different dimers between the family members. Ligand binding and dimerazation initiates various intracellular signaling pathways that affect numerous cellular processes involved in cell survival and proliferation. The oncogenic effects of the EGFR proteins result from amplification, over expression or mutation [60]. Refer to Fig. 1.
