Fibrotic focus: An important parameter for accurate prediction of a high level of tumor-associated macrophage infiltration in invasive ductal carcinoma of the breast

Tumor-Associated Fibrosis Impairs the Response to Immunotherapy

Previously, impaired responses to immunotherapy in cancer had been attributed mainly to inherent tumor characteristics (tumor cell intrinsic factors) such as low immunogenicity, (low) mutational burden, weak host immune system, etc. However, mapping the responses of immunotherapeutic regimes in clinical trials for different types of cancer has pointed towards an obvious commonality - that tumors with a rich fibrotic stroma respond poorly or not at all. This has prompted a harder look on tumor cell extrinsic factors such as the surrounding tumor microenvironment (TME), and specifically, the fibrotic stroma as a potential enabler of immunotherapy failure. Indeed, the role of cancer-associated fibrosis in impeding efficacy of immunotherapy is now well-established. In fact, recent studies reveal a complex interconnection between fibrosis and treatment efficacy. Accordingly, in this review we provide a general overview of what a tumor associated fibrotic reaction is and how it interacts with the members of immune system that are frequently seen to be modulated in a failed immunotherapeutic regime.

Integrated analysis reveals the molecular features of fibrosis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer. High fibrosis, marked by increased collagen fibers, is widespread in TNBC and correlated with tumor progression. However, the molecular features of fibrosis and why it results in a poor prognosis remain poorly understood. Based on multiomics datasets of TNBC, we evaluated the pathological fibrosis grade of 344 samples for further analysis. Genomic, transcriptomic, and immune changes were analyzed among different subgroups of fibrosis. High fibrosis was an independent adverse prognosis predictor and had interactions with low stromal tumor-infiltrating lymphocytes. Genomic analysis identified copy number gains of 6p22.2–6p22.1 (TRIM27) and 20q13.33 (CDH4) as genomic hallmarks of tumors with high fibrosis. Transcriptome analysis revealed the transforming growth factor-beta pathway and hypoxia pathway were key pro-oncogenic pathways in tumors with high fibrosis. Moreover, we systematically evaluate the relationship between fibrosis and different kinds of immune and stromal cells. Tumors with high fibrosis were characterized by an immunosuppressive tumor microenvironment with limited immune cell infiltration and increased fibroblasts. This study proposes new insight into the genomic and transcriptomic alterations potentially driving fibrosis. Moreover, fibrosis is related to an immunosuppressive tumor microenvironment that contributes to the poor prognosis.

CD204-positive macrophages accumulate in breast cancer tumors with high levels of infiltrating lymphocytes and programmed death ligand-1 expression

Although immunotherapy has been demonstrated to be promising in triple-negative (TN) breast cancer (BC), most BC cases are classified as non-TN. To enrich the responders for immunotherapy regardless of their subtypes, classification based on tumor-infiltrating lymphocyte (TIL) levels and programmed death ligand-1 (PD-L1) status may be useful. However, this classification has not been fully applied to BC. Furthermore, suppressive subsets in the local tumor microenvironment, such as tumor-associated macrophages (TAMs), which promote tumor progression, cannot be ignored to overcome immunotherapy resistance. The aims of the present study were to classify primary BC cases based on the TIL levels and PD-L1 status, and to identify suppressive immune subsets in each categorized group. A retrospective analysis of 73 patients with invasive BC was performed. The frequency of TILs was evaluated in HE-stained slides (10% cutoff), and PD-L1 levels (SP142; 1% cutoff), as well as immune subsets (CD3⁺, CD8⁺, FOXP3⁺, CD20⁺, CD68⁺ and CD204⁺ cells) were assessed using immunohistochemistry. It was revealed that 22% (16/73) of the tumors were categorized as TIL⁺PD-L1⁺, of which 69% (11/16) were TN type. By contrast, 66% (48/73) of the tumors were categorized as TIL⁻PD-L1⁻, of which 77% (37/48) were HR⁺ and HER2⁻ types. The number of CD204⁺ M2-type macrophages was significantly associated with high histological grade (P=0.0246) and high Ki-67 (P=0.0152), whereas CD68⁺ macrophages were not associated with these factors. Furthermore, CD204⁺ macrophages and FOXP3⁺ Tregs accumulated in 88% (14/16) and 63% (10/16) of TIL⁺PD-L1⁺ tumors, respectively, compared with 20.8% (10/48) and 27.1% (13/48) of TIL⁻PD-L1⁻ tumors. In conclusion, 22% of BC tumors were classified as TIL⁺PD-L1⁺ (69% were TN), which were enriched with suppressive immune subsets. These cell types may serve as potential novel immunotherapeutic targets.

Association between the degree of fibrosis in fibrotic focus and the unfavorable clinicopathological prognostic features of breast cancer

Objective

To explore the association between the degree of fibrosis in fibrotic focus (FF) and the unfavorable clinicopathological prognostic features of breast cancer.

Methods

A total of 169 cases of breast invasive ductal carcinoma (IDC) were included in the study. Hematoxylin and eosin (H&E) staining was performed in the primary lesion of breast IDC and the degree of fibrosis in tumor-stromal FF was assessed. The association between the degree of fibrosis in FF and the well-known clinicopathologic features of breast cancer was investigated and the influence of the degree of fibrosis in FF on the survival was analyzed.

Results

Tumor size >2 cm (P = 0.023), vascular invasion (P = 0.011), lymphatic vessel invasion (P < 0.001) and HER-2+ (P = 0.032) were positively correlated with the degree of fibrosis in FF in breast IDC. The result of multivariate analysis showed that lymphatic vessel invasion was the only independent correlation factor of high fibrosis in FF in breast IDC (OR = 3.82, 95% CI[1.13 ∼ 12.82], P = 0.031). The Nottingham prognostic index (NPI) of high fibrosis in FF was significantly higher than that of mild and moderate fibrosis in FF in the no vascular infiltration subgroup, the no nerve infiltration subgroup, and the Luminal A subgroup (P = 0.014, 0.039, and 0.018; respectively).

Conclusions

The high fibrosis in FF is closely associated with the strong invasiveness and the high malignancy of breast IDC. The degree of fibrosis in FF might be considered as a very practical and meaningful pathological feature of breast cancer.