Biology of breast cancer in Nigerian women: a pilot study

BACKGROUND

Compared to the developed world, there are relatively few studies that describe the tumor biology of breast cancer in African women. While little is known about the tumor biology, clinical and epidemiologic studies suggest that breast cancer in African women are characterized by presentation at late stage and poor clinical outcomes. Analysis of the biological features of breast cancers in Nigerian women was designed to bring additional insight to better understand the spectrum of disease, the phenotypes that present, and the types of interventions that might improve outcomes.

MATERIALS AND METHODS

We performed histological analyses for hormone receptors (estrogen and progesterone receptors), HER2, and tumor infiltrating macrophages (TAM) on 17 breast cancers, obtained from Abia State University Teaching Hospital (Aba, Nigeria), between November 2008 and October 2009. On a subset of these cases, we investigated the potential role of a virus in the etiology of these aggressive cancers.

RESULTS

The majority of cases in this cohort were characterized as high grade (100% were grade III), triple-negative (65%), and occur in young women (mean age 47 years). We observed high infiltration of TAMs in these tumors, but no evidence of a viral etiology.

CONCLUSION

Our findings indicate that breast cancers in Nigerian women have a highly aggressive phenotype (high grade, hormone receptor negative), which is similar to other studies from Africa and other developing nations, as well as from African American women, but is significantly different from Caucasian women in the developed world. The presence of high numbers of TAMs in these tumors raises the possibility of targeting the immune microenvironment for therapeutic interventions.

Elevated levels of proliferating and recently migrated tumor-associated macrophages confer increased aggressiveness and worse outcomes in breast cancer

PURPOSE

Macrophages play a major role in inflammatory processes and have been associated with poor prognosis in a variety of cancers, including breast cancer. Previously, we investigated the relationship of a subset of tumor-associated macrophages (PCNA(+) TAMs) with clinicopathologic characteristics of breast cancer. We reported that high PCNA(+) TAM counts were associated with hormone receptor (HR)-negative, high-grade tumors and early recurrence. To further understand the significance of elevated PCNA(+) TAMs and the functionality of TAMs, we examined the expression of S100A8/S100A9 with the antibody Mac387. The heterodimeric S100A8/S100A9 complex plays a role in inflammation and is increased in several cancer types.

METHODS

We performed immunohistochemistry using the Mac387 antibody on 367 invasive human breast cancer cases. Results were compared to previous PCNA(+) TAM counts and were correlated with patient outcomes adjusting for HR status and histologic grade.

RESULTS

Like PCNA(+) TAMs, high Mac387 counts were associated with HR negativity, high tumor grade, younger age, and decreased recurrence-free survival. Mac387, however, appears to identify both a subset of macrophages and a subset of tumor cells. The concordance between Mac387 and PCNA(+) TAM counts was low and cases that had both high Mac387 and high PCNA(+) TAMs counts had a stronger association with early recurrence.

CONCLUSIONS

The presence of high numbers of PCNA(+) TAMs and Mac387-positive cells in breast cancers with poor outcomes may implicate a subset of TAMs in breast cancer pathogenesis, and may ultimately serve to develop potential cellular targets for therapeutic interventions.

Elevated PCNA+ tumor-associated macrophages in breast cancer are associated with early recurrence and non-Caucasian ethnicity

African American and Hispanic women develop more triple negative breast cancer at younger ages than Caucasian women. The frequently observed association between race and socioeconomic status (SES) has confounded our understanding of the outcomes disparities seen in these groups. Given the association between inflammatory cells and high-grade, triple negative tumors, we sought to investigate whether differences in the presence of these cells varies by race. We evaluated breast tumor specimens for the presence PCNA+ tumor-associated macrophages (TAMs) in consecutive cases from a county hospital serving primarily un- or under-insured patients. All patients in this cohort had elevated PCNA + TAM levels. Higher PCNA + TAM counts were associated with hormone receptor (HR) negative tumors and non-Caucasian ethnicity. Hispanic women specifically had significantly higher PCNA + TAM counts than Caucasian patients and shorter disease-free survival. These findings implicate immune function in the development of aggressive breast cancer and suggest a possible link between SES and the inflammatory response.

Tumor-associated macrophages in breast cancer as potential biomarkers for new treatments and diagnostics

While several inflammatory cell types participate in cancer development, macrophages specifically play a key role in breast cancer, where they appear to be part of the pathogenesis of high-grade tumors. Tumor-associated macrophages (TAMs) produce factors that promote angiogenesis, remodel tissue and dampen the immune response to tumors. Specific macrophage types contribute to increased metastases in animal models, while human studies show an association between TAMs and tumors with poor prognostic features. Macrophages display a spectrum of phenotypic states, with the tumor microenvironment skewing TAMs towards a 'nonclassical' activation state, known as the M2, or wound healing/regulatory state. These TAMs are found in high-risk breast cancers, making them an important therapeutic target to explore. Improved techniques for identifying TAMs should translate into clinical applications for prognosis and treatment.

Abstract P5-04-01: Expression of Genes Associated with the Innate Immune System and Response to Neoadjuvant Chemotherapy in Breast Cancer

Background: The efficacy of cancer chemotherapy is generally assessed by the ability to directly kill or inhibit the growth of cancer cells. However, there is evidence suggesting that anticancer immune responses also contribute to the efficacy of conventional chemotherapy. Recent studies have shown that chemotherapeutic agents (anthracyclines in particular) can elicit innate immune responses via the release of proteins from dying tumor cells that interact with Toll-like receptors (TLR) on macrophages (mΦ) and dendritic cells (DC). The subsequent induction of cytotoxic T cell responses leads to the elimination of residual cancer cells not killed by the chemotherapy. To test this idea of chemotherapy-induced immunogenic cell death in breast cancer, we examined gene expression data for women with breast cancer treated neoadjuvantly, starting with adriamycin, on the I-SPY TRIAL (2003-2006), to see if genes that predict this type of immune response would also predict complete pathologic response (pCR) Methods: A panel of 47 genes were selected, including those expressed by the cancer cells as well as infiltrating immune cells: TLR/mΦ/DC activating proteins, TLR signaling genes, chemokines & chemokine receptors, cytokines & cytokine receptors, and mO, DC, & T cells markers. This gene set was then evaluated using expression array data from the I-SPY TRIAL, available on both Affymetrix (n=) and Agilent (n= 153) platforms. Initial analyses were performed using the UCSC Cancer Genomics Browser, a suite of web-based tools to integrate, visualize and analyze cancer genomics/expression data and clinical data. Differentially expressed genes were compared between patients who achieved a pathological complete response (pCR) following neoadjuvant chemotherapy vs. those who did not. A second independent data set available on the Cancer Genomics browser served as a validation set. These data, from MD Anderson, included 133 patients treated with neoadjuvant therapy (TFAC) with available Affymetrix array data.

Results: Of the 47 selected genes, 1 was not present on the Affymetrix array and 7 were absent from the Agilent array. Twelve of the 46 genes (26%) on the Affymetrix array and 20 of the 40 genes (50%) on the Agilent array were significantly differentially expressed comparing responders vs. non-responders. Overall, 25 of the 47 genes (53%) were differentially expressed on one or both arrays. Gene set enrichment and Paradigm pathway inference analyses confirmed that these genes are significantly enriched among responders. In the validation set, 20 of 46 genes (43%) were significantly differentially expressed.

Conclusion: We identified a panel of genes associated with immunogenic cell death and demonstrated their differential expression in patients who responded to neoadjuvant chemotherapy vs. non-responders. These results suggest a role for the host immune system in the response to chemotherapy. If the success of currently used chemotherapies depends on synergistic interactions with the immune system, then a better understanding of the mechanisms involved in chemotherapy-induced immunogenic cell death will provide a foundation for the design of novel chemo-immunotherapeutic strategies for breast cancer treatment.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-04-01.