Cytokine Expression During Radiation for Breast Cancer

It is well recognized that the diagnostic and therapeutic gains made in the management of breast cancer over the last 2 decades are not fully realized by all groups. African American women with breast cancer have greater risk of recurrence, shorter overall survival, shorter survival after relapse, worse toxicity and worse cosmetic outcome than their Caucasian counterparts. These differences in outcome persist even when controlling for age, and stage at presentation. Being similarly treated with modern breast conserving therapy (lumpectomy and adjuvant whole breast irradiation) at recognized centers of excellence does little to alleviate the disparities in outcomes. Controlling for socioeconomic factors decreases the severity of these disparities, but it does not completely explain them. Theories abound as to the cause of outcome inequality. Many of these theories take either a psychosocial, or biologic bent. One potential biologic cause may be chemokine and cytokine expression.

Chemokines and cytokines (chemo/cytokines) are proteins and peptides used for cell signaling. Primarily secreted by T cells and macrophages, they influence cellular activation, differentiation, and function and act as mediators for inflammatory and immune responses. There has been substantial research linking some of these chemo/cytokines [Tumor necrosis factor alpha (TNFα), platelet derived growth factor (PDGF), Transforming growth factor beta (TGFβ), interleukin (IL)-6,and IL-8] to tumor promotion and progression. For example, TNFα has been linked to greater cell survival despite genomic injury which in turn leads to greater genetic alterations and malignant transformation. TNFα has been associated with breast cancer progression and metastases. Blocking the receptor for PDGF appears to decrease the metastatic potential of breast cancer cell lines. TGFβ inhibits T cell and B cell lymphocytes and natural killer cell cytotoxicity. This immuno-suppression has been shown to promote tumor progression in mammary cancer cells lines. The ability of TGFβ to promote tumor progression is so well recognized that it has become a therapeutic target by some researchers. Interferon gamma (IFNγ) has been shown to inhibit mammary cancer cell proliferation and angiogenesis in vitro and in vivo. Clinically, Lyon et al reported significantly higher circulating levels of TNFα, IL-6, and IL-8 in women with breast cancer compared to women with a negative breast biopsy. Additionally, researchers have directly correlated increased levels of IL-6 with the development and progression of breast cancer, and decreased overall survival (OAS). Conclusion: Expression of certain chemokines and cytokines is associated with development and progression of breast cancer.