p-STAT3 expression in breast cancer correlates negatively with tumor size and HER2 status

The interferon/STAT1 signaling axis is a common feature of tumor-initiating cells in breast cancer

A tumor cell subpopulation of tumor-initiating cells (TIC), or "cancer stem cells", are associated with therapeutic resistance, as well as both local and distant recurrence. Enriched populations of TIC are identified by markers including aldehyde dehydrogenase (ALDH1) activity, the cell surface marker combination CD44 + /CD24 - , or fluorescent reporters for signaling pathways that regulate TIC function. We showed previously that S ignal T ransducer and A ctivator of T ranscription (STAT)-mediated transcription allows enrichment for TIC in claudin-low models of human triple-negative breast cancer using a STAT-responsive reporter. However, the molecular phenotypes of STAT TIC are not well understood, and there is no existing method to lineage-trace TIC as they undergo cell state changes. Using a new STAT-responsive lineage-tracing (LT) system in conjunction with our original reporter, we enriched for cells with enhanced mammosphere-forming potential in some, but not all, basal-like triple-negative breast cancer (TNBC) xenograft models (TNBC) indicating TIC-related and TIC-independent functions for STAT signaling. Single-cell RNA sequencing (scRNAseq) of reporter-tagged xenografts and clinical samples identified a common interferon (IFN)/STAT1-associated transcriptional state, previously linked to inflammation and macrophage differentiation, in TIC. Surprisingly, most of the genes we identified are not present in previously published TIC signatures derived using bulk RNA sequencing. Finally, we demonstrated that bone marrow stromal cell antigen 2 (BST2), is a cell surface marker of this state, and that it functionally regulates TIC frequency. These results suggest TIC may exploit the IFN/STAT1 signaling axis to promote their activity, and that targeting this pathway may help eliminate TIC.

Significance

TIC differentially express interferon response genes, which were not previously reported in bulk RNA sequencing-derived TIC signatures, highlighting the importance of coupling single-cell transcriptomics with enrichment to derive TIC signatures.

Role of CTLA4 and pSTAT3 Immunostaining in Prognosis and Treatment of the Colorectal Carcinoma

Background & Objective

Colorectal carcinoma (CRC) is the third leading cause of cancer-caused death worldwide and constitutes about 6.48% of all malignancies in Egypt. Studying the molecular profile of CRC is essential for developing targeted therapies. STAT3 and CTLA4 expression are considered as molecular abnormalities involved in the CRC progression and chemo-resistance. Therefore, they could be used as potential therapeutic targets. This study aimed to evaluate pSTAT3 and CTLA4 expression levels and their possible roles as prognostic and predictive biomarkers in CRC using immunohistochemistry (IHC).

Methods

This retrospective study included 113 CRC patients. Tissue microarrays were constructed, followed by pSTAT3 and CTLA4 antibodies immunostaining. Their expression was assessed and compared with the clinicopathological parameters and survival data.

Results

Both pSTAT3 and CTLA4 overexpression were significantly associated with poor prognostic parameters, such as the presence of distant metastasis (P=0.02 & 0.03), high grade (P<0.001 & 0.03), high mitotic count (P<0.001 & 0.03), high tumor budding group (P=0.008 & 0.04), infiltrating tumor border (P<0.001 & 0.007) respectively, and advanced pathological stage with pSTAT3 (P=0.02). A significant association was found between overexpression of both markers and short overall survival. Correlations between the H-score of pSTAT3 and CTLA4 in CRC showed a significant positive correlation (P<0.001).

Conclusion

STAT3 and CTLA4 positivity may be linked to the development and progression of the CRC, and they may provide potential prognostic indicators and therapeutic targets for CRC patients.

STAT3 Signaling in Breast Cancer: Multicellular Actions and Therapeutic Potential

Simple Summary

Many signaling pathways are overactive in breast cancer, and among them is the STAT3 signaling pathway. STAT3 is activated by secreted factors within the breast tumor, many of which are elevated and correlate to advanced disease and poor survival outcomes. This review examines how STAT3 signaling is activated in breast cancer by the proinflammatory, gp130 cytokines, interleukins 6 and 11. We evaluate how this signaling cascade functions in the various cells of the tumor microenvironment to drive disease progression and metastasis. We discuss how our understanding of these processes may lead to the development of novel therapeutics to tackle advanced disease.

Abstract

Interleukin (IL)-6 family cytokines, such as IL-6 and IL-11, are defined by the shared use of the gp130 receptor for the downstream activation of STAT3 signaling and the activation of genes which contribute to the “hallmarks of cancer”, including proliferation, survival, invasion and metastasis. Increased expression of these cytokines, or the ligand-specific receptors IL-6R and IL-11RA, in breast tumors positively correlate to disease progression and poorer patient outcome. In this review, we examine evidence from pre-clinical studies that correlate enhanced IL-6 and IL-11 mediated gp130/STAT3 signaling to the progression of breast cancer. Key processes by which the IL-6 family cytokines contribute to the heterogeneous nature of breast cancer, immune evasion and metastatic potential, are discussed. We examine the latest research into the therapeutic targeting of IL-6 family cytokines that inhibit STAT3 transcriptional activity as a potential breast cancer treatment, including current clinical trials. The importance of the IL-6 family of cytokines in cellular processes that promote the development and progression of breast cancer warrants further understanding of the molecular basis for its actions to help guide the development of future therapeutic targets.