Breast Cancer Subtypes, Associated Biomarkers, and the Involvement of Human Papilloma Virus in Ethiopian Population
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Date
2023-12-22
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Addis Ababa University
Abstract
Breast cancer is the most common type of cancer in the world as well as in Ethiopia.
Although research on breast cancer in Ethiopia has been conducted, none of them have
evaluated breast cancer in multiple regions of the country, which is important considering
Ethiopia’s enormous ethnic and genetic diversity. Hence, this study was carried out to
evaluate the distribution of breast cancer subtypes and associated immune cell biomarkers,
hormone receptors, matrix metalloproteinases (MMPs), and HPV genotypes in selected
Ethiopian regions.
A total of 227, 81, 58, and 120 formalin-fixed paraffin-embedded (FFPE) tissue blocks
were collected for breast cancer subtyping, immune cell biomarkers analysis, MMP
expression, and HPV genotyping, respectively. Immunohistochemistry (IHC) staining was
performed for breast cancer subtyping based on estrogen receptor (ER), progesterone
receptor (PR), human epidermal growth factor receptor 2 (HER-2), and Ki-67 proliferation
markers, and for additional immune cell biomarker expression. RNA was extracted and
quantitative reverse-transcription PCR was performed for MMP expression analysis. DNA
was extracted from archived FFPE breast tissue specimens and target genes were amplified
using PCR for HPV genotyping. SPSS Version 25 was used to enter and analyze data. For
immune cell biomarkers and MMP results, GraphPad Prism version 8.0.0 was used for
statistical analysis.
A large percentage of breast cancers were found to have advanced clinical and pathologic
features, such as substantial lymph node involvement, large tumor size, and high
histological grade. The percentage of ER and PR-negative tumors were 48.3% and 53.2%,
respectively. The IHC subtype distribution was 33.1% triple-negative (ER-, PR-, HER-2-)
breast cancer, 27.6% luminal B ((ER+, PR+, HER-2- and Ki-67 ≥ 20%) or (ER+, PR+, and
HER-2+)), 25.2% luminal A (ER+, PR+, HER-2- and Ki-67< 20%), and 14.1% HER-2-
enriched (ER-, PR-, HER-2+). In multiple logistic regression analysis, grade III and HER-
2 positivity were associated with larger tumor size, and tumor size was also higher in
samples from Southwestern Ethiopia (Jimma) as compared to Northern Ethiopia (Mekele).
The MMP-11 expression levels were significantly higher in breast cancer cases than in
benign breast tumors (P=0.012).
The non-luminal (triple-negative and HER-2-enriched) breast cancer subtype had a higher
percentage of stromal CD20+, intratumoral CD3+ tumor-infiltrating lymphocytes, and
CD68+ tumor-associated macrophages than the luminal (Luminal A and Luminal B)
subtype. The stromal programmed cell death ligand 1 (PD-L1) +, intratumoral CD3+
tumor-infiltrating lymphocytes, CD163+ tumor-associated macrophages, and PD-L1+
were also more commonly found in grade III breast cancer than in grade I and II breast
cancer, respectively. Human papillomavirus was found in 20.6% of breast cancer patients
and 29.6% of non-malignant breast tumors. Human papillomavirus infection was nearly
10-fold more common in ER-positive than ER-negative breast cancer.
A considerably high prevalence of triple-negative breast cancer was reported in our study,
demanding additional research that includes identifying genetic predisposition factors. A
significant association was found between the breast cancer subtype and stromal CD20+,
intratumoral CD3+ tumor-infiltrating lymphocytes, and CD68+ tumor-associated
macrophages. The stromal PD-L1+, intratumoral CD3+ tumor-infiltrating lymphocytes,
CD163+ tumor-associated macrophages, and PD-L1+ were also associated with tumor
grade. Our findings suggest an important impact of MMPs in breast cancer
pathophysiology, particularly MMP-11. This study also showed no proof of a link between
HPV infection and breast cancer; however, the finding that HPV was more prevalent in
breast tumors that were ER-positive than ER-negative warrants further attention.
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Keywords
Breast Cancer, Estrogen Receptor, HER-2, HPV Genotype, IHC Subtype, Immunohistochemistry, MMP, Tumor-Associated Macrophages, Tumor-Infiltrating Lymphocytes, and Triple-Negative