The advent of immune-checkpoint inhibitors (ICI) in modern oncology has significantly improved survival in several cancer settings. A subgroup of women with breast cancer (BC) has immunogenic infiltration of lymphocytes with expression of programmed death-ligand 1 (PD-L1). These patients may potentially benefit from ICI targeting the programmed death 1 (PD-1)/PD-L1 signaling axis. The use of tumor-infiltrating lymphocytes (TILs) as predictive and prognostic biomarkers has been under intense examination. Emerging data suggest that TILs are associated with response to both cytotoxic treatments and immunotherapy, particularly for patients with triple-negative BC. In this review from The International Immuno-Oncology Biomarker Working Group, we discuss (a) the biological understanding of TILs, (b) their analytical and clinical validity and efforts toward the clinical utility in BC, and (c) the current status of PD-L1 and TIL testing across different continents, including experiences from low-to-middle-income countries, incorporating also the view of a patient advocate. This information will help set the stage for future approaches to optimize the understanding and clinical utilization of TIL analysis in patients with BC.

Multiple copies of the mitochondrial genome in eukaryotic cells are organized into protein-DNA complexes called nucleoids. Mitochondrial genome repair mechanisms have been reported, but they are less well characterized than their nuclear counterparts. To expand our knowledge of mitochondrial genome maintenance, we have studied the localization of the BRCA1 protein, known to be involved in nuclear repair pathways. Our confocal and immunoelectron microscopy results show that BRCA1 is present in mitochondria of several human cancer cell lines and in primary breast and nasal epithelial cells. BRCA1 localization in mitochondria frequently overlapped that of nucleoids. Small interfering RNAmediated knockdown of BRCA1 in human cancer cells (confirmed by Western blot) results in decreased nuclear, cytoplasmic, and mitochondrial staining after immunofluorescence microscopy, establishing the specificity of the BRCA1 immunolabeling. Furthermore, using cell fractionation, dephosphorylation, and enzyme protection experiments, we show that a 220-kDa phosphorylated isoform of BRCA1 is enriched in mitochondrial and nuclear fractions but reduced in cytoplasmic subcellular fractions. Submitochondrial fractionation confirmed the presence of BRCA1 protein in isolated mitoplasts. Because phosphorylation of BRCA1 and subsequent changes in subcellular localization are known to follow DNA damage, our data support a universal role for BRCA1 in the maintenance of genome integrity in both mitochondria and nucleus.

Heregulin-alpha is a motility factor that is produced and released by normal epidermal keratinocytes and thus plays a key role in the pathogenesis of Paget's disease. Paget cells express heregulin receptors HER2/NEU, as well as HER3 and/or HER4, both of which function as a co-receptor of HER2/NEU. Binding of heregulin-alpha to the receptor complex on Paget cells results in the chemotaxis of these breast cancer cells, which eventually migrate into the overlying nipple epidermis.

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Wound healing is a complex process of which growth and motility are essential features. The aim of this study was to search for keratinocyte-derived secreted factors that may play a role in these mechanisms, and their corresponding receptors. Growth and motility factors were purified from conditioned medium from cultured primary keratinocytes. Receptor and growth factor expression profiles were investigated by immunohistochemical, western blotting, and in situ hybridization analysis on cultured keratinocytes and tissue sections derived from chronic wounds. The most potent autocrine growth factor for keratinocytes, which it was possible to purify and sequence from keratinocyte-conditioned medium, is amphiregulin. Its receptor HER-1 is up-regulated on the membranes of keratinocytes lining the edge of the wound. From the same keratinocyte-conditioned medium, heregulin-alpha was purified as a potent motility factor for keratinocytes. Its receptor is HER-3, which is up-regulated on the membranes of keratinocytes lining the edge of the wound and on keratinocytes that had migrated towards the centre of the wound. HER-4 - another receptor for heregulin-alpha - is weakly present in occasional cells near the edge of the wound. The co-receptor for HER-3 and HER-4 is HER-2/neu, which is also present in epidermal cells but not overexpressed. This study shows that heregulin-alpha is a potent motility factor for normal epithelial cells and that it plays a central role in the process of wound healing of stratified epithelia. Heregulin-alpha has already been shown to be the motility factor leading to migration of HER-2/neu-overexpressing breast cancer cells. The role of amphiregulin as a growth factor and of heregulin-alpha as a motility factor for keratinocytes in epidermal and mucosal wound healing parallels their motility and growth induction in carcinogenesis.

Histopathological assessment of ductal carcinoma in situ (DCIS), a non-obligate precursor of invasive breast cancer, is characterized by considerable inter-observer variability. Previously, post hoc dichotomization of multi-categorical variables was used to determine the 'ideal' cut-offs for dichotomous assessment. The present international multi-center study evaluated inter-observer variability among 39 pathologists who performed upfront dichotomous evaluation of 149 consecutive DCIS.All pathologists independently assessed nuclear atypia, necrosis, solid DCIS architecture, calcifications, stromal architecture and lobular cancerization in one digital slide per lesion. Stromal inflammation was assessed semi-quantitatively. Tumor-infiltrating lymphocytes (TILs) were quantified as percentages and dichotomously assessed with a cut-off at 50%. Krippendorff's alpha (KA), Cohen's kappa and intraclass correlation coefficient were calculated for the appropriate variables.Lobular cancerization (KA = 0,396), nuclear atypia (KA = 0,422) and stromal architecture (KA = 0,450) showed the highest inter-observer variability. Stromal inflammation (KA = 0,564), dichotomously assessed TILs (KA = 0,520) and comedonecrosis (KA = 0,539) showed slightly lower inter-observer disagreement. Solid DCIS architecture (KA = 0,602) and calcifications (KA = 0,676) presented with the lowest inter-observer variability. Semi-quantitative assessment of stromal inflammation resulted in a slightly higher inter-observer concordance than upfront dichotomous TILs assessment (KA = 0,564 versus KA = 0,520). High stromal inflammation corresponded best with dichotomously assessed TILs when the cut-off was set at 10% (kappa = 0,881). Nevertheless, a post hoc TILs cut-off set at 20% resulted in the highest inter-observer agreement (KA = 0,669).Despite upfront dichotomous evaluation, the inter-observer variability remains considerable and is at most acceptable, although it varies among the different histopathological features. Future studies should investigate its impact on DCIS prognostication. Forthcoming machine learning algorithms may be useful to tackle this substantial diagnostic challenge.

Hyperplasia without and with atypia is considered to be a precursor lesion for certain breast carcinomas. The cytogenetic events and the molecular pathology involved in the multistep process from normal to invasive carcinoma are unknown. To characterise the sequence of early genetic abnormalities of chromosome 17q and their biological consequences in the pathogenesis of breast cancer, we performed immunohistochemistry on 451 breast tissues including 180 normal breast specimens, 28 hyperplastic lesions without atypia and 44 with atypia, 100 cases of ductal carcinoma in situ (DCIS) and 99 cases of invasive ductal carcinoma. We correlated the overexpression of the c-ErbB-2 protein, the histological and the recently proposed differentiation classification of DCIS with the extent of DCIS. For fluorescence in situ hybridisation (FISH) analysis, different probes spanning the 17q region including the c-erbB-2 gene locus and those which are found adjacent, were used. Reverse painting and comparative genomic hybridisation (CGH) were performed on several breast cancer cell lines. c-ErbB-2 overexpression was observed in only 29% of DCIS and 23% of invasive carcinomas, but not in hyperplastic and normal tissue. c-ErbB-2 overexpression is correlated with poor differentiation in DCIS but not in invasive carcinoma. In DCIS, there was no correlation with the histological subtype classification. The average extent of DCIS is significantly increased from 13.81 mm in c-ErbB-2 negative cases to 29.37 mm in c-ErbB-2 positive cases. The increase was considered to be a possible consequence of the overexpression and is probably due to the previously described motility enhancing effect of the c-ErbB-2 protein. The histological and differentiation classification of DCIS did not correlate with the extent of disease. Using FISH, amplified genes at 17q12, always including the c-erbB-2 gene, were detected in all cases of DCIS and invasive carcinoma with c-ErbB-2 overexpression. The centromeric region and the NF1 locus, which is located between the centromere and c-erbB-2, were not amplified in any of the DCIS and invasive breast carcinomas, but co-amplification of the myeloperoxidase gene was detected in 3/5 DCIS and 1/5 invasive carcinomas with c-ErbB-2 overexpression. In contrast to c-erbB-2, immunohistochemical overexpression of their respective gene products was not observed. FISH, reverse painting and CGH show similar amplified genes with amplified c-erbB-2 in c-ErbB-2 overexpressing SK-BR-3 and BT474 human breast cancer cells. The amplified genes are part of two different amplicons. Extensive modifications of the 17q chromosomal region, caused by translocation, were also observed in these cell lines. It is concluded that the modifications of chromosome 17q, inducing overexpression of c-ErbB-2 protein, occur at the level of transition from hyperplasia to DCIS. They are preserved in invasive carcinoma with overexpression of c-ErbB-2 protein. This had led to the hypothesis that these modifications at 17q may lead to a larger extent of DCIS.

The aim of this prospective study was to evaluate biological markers, their correlation with response and outcome, and the change in these markers under the influence of preoperative chemotherapy (PCT) in patients with a large primary breast cancer. One hundred and thirty-five women were treated with PCT, followed by locoregional therapy and adjuvant treatment. Estrogen receptor (ER), progesterone receptor (PgR), HER-2, p53, and cathepsin D were determined by immunohistochemistry (IHC) before and after PCT. The overall response (OR) was 70% and the pathologic complete response (pCR) was 13%. Forty-four percent of the patients could be offered breast-conserving surgery (BCS). At a median follow-up of 50 mo the overall survival is 82% and the disease-free survival is 70%. No local recurrence (LR) has developed following BCS. Invasive ductal carcinoma (IDC) was more frequently ER-negative and HER-2-positive than invasive lobular carcinoma (ILC). P53-negative and ER-negative patients seemed to be more chemosensitive compared to p53-positive patients (74% vs 53%) and ER-positive patients (75% vs 65%), but this difference did not reach statistical significance. A trend toward higher complete pathologic remission rate was seen for ER-negative patients (p = 0.0609). PgR, HER-2, and cathepsin D were not related to response. The pattern of biological markers did not change with PCT, making repeated determination useless.