Regulatory T cells: Their role in triple-negative breast cancer progression and metastasis.

Triple-negative breast cancer (TNBC) is an aggressive and immunogenic subtype of breast cancer. This tumorigenicity is independent of hormonal or HER2 pathways because of a lack of respective receptor expression. TNBC is extremely prone to drug resistance and early recurrence because of T-regulatory cell (Treg) infiltration into the tumor microenvironment (TME) in addition to other mechanisms like genomic instability. Tumor-infiltrating Tregs interact with both tumor and stromal cells as well as extracellular matrix components in the TME and induce an immune-suppressive phenotype. Hence, treatment of TNBC with conventional therapies remains challenging. Understanding the protective mechanism of Tregs in shielding TNBC from antitumor immune responses in the TME will pave the way for developing novel, immune-based therapeutics. The current review focuses on the role of tumor-infiltrating Tregs in tumor progression and metabolic reprogramming of the TME. The authors have extended their focus to oncotargeting Treg-mediated immune suppression in breast cancer. Because of its potential role in the TME, modulating Treg activity may provide a novel strategic intervention to combat TNBC. Both under laboratory conditions and in clinical trials, currently available anticancer drugs and natural therapeutics as potential agents for targeting Tregs are explored.

Malla RR ，Vasudevaraju P ，Vempati RK ，Rakshmitha M ，Merchant N ，Nagaraju GP ... -  《-》

3D Collagen Fiber Concentration Regulates Treg Cell Infiltration in Triple Negative Breast Cancer.

Triple negative breast cancer (TNBC) is characterized by poor prognosis and a lack of effective therapeutic agents owing to the absence of biomarkers. A high abundance of tumor-infiltrating regulatory T cells (Tregs) was associated with worse prognosis in malignant disease. Exploring the association between Treg cell infiltration and TNBC will provide new insights for understanding TNBC immunosuppression and may pave the way for developing novel immune-based treatments. Patients from TCGA were divided into Treg-high (Treg-H) and Treg-low (Treg-L) groups based on the abundance of Tregs according to CIBERSORT analysis. The association between expression level of Tregs and the clinical characteristics as well as prognosis of breast cancer were evaluated. Next, a Treg-related prognostic model was established after survival-dependent univariate Cox and LASSO regression analysis, companied with an external GEO cohort validation. Then, GO, KEGG and GSEA analyses were performed between the Treg-H and Treg-L groups. Masson and Sirius red/Fast Green staining were applied for ECM characterization. Accordingly, Jurkat T cells were encapsulated in 3D collagen to mimic the ECM microenvironment, and the expression levels of CD4, FOXP3 and CD25 were quantified according to immunofluorescence staining. The expression level of Tregs is significantly associated with the clinical characteristics of breast cancer patients, and a high level of Treg cell expression indicates a poor prognosis in TNBC. To further evaluate this, a Treg-related prognostic model was established that accurately predicted outcomes in both TCGA training and GEO validation cohorts of TNBC patients. Subsequently, ECM-associated signaling pathways were identified between the Treg-H and Treg-L groups, indicating the role of ECM in Treg infiltration. Since we found increasing collagen concentrations in TNBC patients with distant migration, we encapsulated Jurkat T cells within a 3D matrix with different collagen concentrations and observed that increasing collagen concentrations promoted the expression of Treg biomarkers, supporting the regulatory role of ECM in Treg infiltration. Our results support the association between Treg expression and breast cancer progression as well as prognosis in the TNBC subtype. Moreover, increasing collagen density may promote Treg infiltration, and thus induce an immunosuppressed TME.

Gao H ，Tian Q ，Zhou Y ，Zhu L ，Lu Y ，Ma Y ，Feng J ，Jiang Y ，Wang B ... -  《Frontiers in Immunology》

Regulatory T cells are associated with the tumor immune microenvironment and immunotherapy response in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with a high risk of distant metastasis, an extremely poor prognosis, and a high risk of death. Regulatory T cells (Tregs) contribute to the formation of a tumor immunosuppressive microenvironment, which plays an important role in the progression and treatment resistance of TNBC. A public single-cell sequencing dataset demonstrated increased infiltration of Tregs in TNBC tissues relative to normal breast tissue. Weighted gene co-expression network analysis was used to identify Treg infiltration-related modules for METABRIC TNBC samples. Subsequently, we obtained two Treg infiltration-associated clusters of TNBC by applying consensus clustering and further constructed a prognostic model based on this Treg infiltration-associated gene module. The ability of the selected gene in the prognostic model, thymidine kinase-1 (TK1), to promote the progression of TNBC was evaluated in vitro. We concluded that two Treg infiltration-associated clusters had different prognoses and sensitivities to drugs commonly used in breast cancer treatment, and multi-omics analysis revealed that the two clusters had different copy number variations of key tumor progression genes. The 7-gene risk score based on TNBC Treg infiltration was a reliable prognostic indicator both in the training and validation cohorts. Moreover, patients with TNBC with high Treg infiltration-related scores lacked the activation of immune activation pathways and exhibited resistance to anti-PD1 immunotherapy. Knocking down TK1 led to impaired proliferation, migration, and invasion of TNBC cells in vitro. In addition, specimens from patients with TNBC with high TK1 expression showed significantly higher Treg infiltration in tumors. Results of spatial transcriptome analysis showed that TK1 positive cells mainly localize in tumor area, and Treg cell infiltration in TNBC tissues was associated with high expression of TK1. Pan-cancer analysis also demonstrated that TK1 is associated with poor prognosis and activation of proliferation pathways in multiple cancers. We established a prognostic model related to Treg infiltration and this model can be used to establish a clinically relevant classification of TNBC progression. Additionally, our work revealed the underestimable potential of TK1 as a tumor biomarker and immunotherapeutic target.

Huang P ，Zhou X ，Zheng M ，Yu Y ，Jin G ，Zhang S ... -  《Frontiers in Immunology》

Tumor microenvironment: Challenges and opportunities in targeting metastasis of triple negative breast cancer.

Triple negative breast cancer (TNBC) is most aggressive subtype of breast cancers with high probability of metastasis as well as lack of specific targets and targeted therapeutics. TNBC is characterized with unique tumor microenvironment (TME), which differs from other subtypes. TME is associated with induction of proliferation, angiogenesis, inhibition of apoptosis and immune system suppression, and drug resistance. Exosomes are promising nanovesicles, which orchestrate the TME by communicating with different cells within TME. The components of TME including transformed ECM, soluble factors, immune suppressive cells, epigenetic modifications and re-programmed fibroblasts together hamper antitumor response and helps progression and metastasis of TNBCs. Therefore, TME could be a therapeutic target of TNBC. The current review presents latest updates on the role of exosomes in modulation of TME, approaches for targeting TME and combination of immune checkpoint inhibitors and target chemotherapeutics. Finally, we also discussed various phytochemicals that alter genetic, transcriptomic and proteomic profiles of TME along with current challenges and future implications. Thus, as TME is associated with the hallmarks of TNBC, the understanding of the impact of different components can improve the clinical benefits of TNBC patients.

Deepak KGK ，Vempati R ，Nagaraju GP ，Dasari VR ，S N ，Rao DN ，Malla RR ... -  《-》

Ethnic disparities in the immune microenvironment of triple negative breast cancer and its role in therapeutic outcomes.

In 2020, newly diagnosed breast cancer (BC) cases surpassed that of lung cancer among women, making it the most common female cancer globally. In spite of recent increases in incidence rates, mortality due to BC has declined since 1989. These declines have been attributed to advancements in treatment modalities as well as increased mammography surveillance. Despite these advances, African American (AA) women are 40% more likely to die from BC than Caucasian women. Multifactorial etiology has been implicated in the disparity of BC mortality rates among AA women. As an example, AA women have a disproportionate incidence of triple negative breast cancer (TNBC), which has a poor prognosis and marginal treatment options. Increasingly, the tumor microenvironment (TME) has gained relevance as it relates to primary tumor progression, metastasis and treatment possibilities. The treatment outcomes or pathological complete response (pCR) in TNBC among AA women are affected by differences in TME. The TME of AA women exhibit several variances in acellular and cellular components associated with pro-tumorigenic effects. For example, increased levels of the adipocyte-related hormone, resistin, the pro-inflammatory cytokine, IL-6, and the CC chemokine, CCL2, within the TME of AA women gives rise to an increased density of M2 macrophages, also known as tumor-associated macrophages. Elevated levels of vascular endothelial growth factor in the TME of AA women increase the vascular density or vascularity, which facilitate aggressive tumor growth and metastasis. Furthermore, a pro-tumorigenic TME is supported by increased levels of the CXC chemokine, CXCL12 that results in the recruitment of regulatory T lymphocytes (Tregs ). Due to these and other differences in the TME of AA women, precision oncology can target specific aspects of the TME that may contribute to a poorer prognosis. In addition to the discrepancies in the TME, AA women face socio-economic barriers that limit their ability to access state-of-the-art, novel therapies against metastatic TNBC. In this review, we will provide a brief overview of the tumor immune microenvironment, immune-based treatment options for TNBC and their potential to decrease health disparities due to ethnicity.

Zajac KK ，Malla S ，Babu RJ ，Raman D ，Tiwari AK ... -  《Cancer Reports》