Exosomes From The Tumor Microenvironment Promote Breast Cancer Progression And Therapy Resistance Through Unshielded Non-Coding Rna

Breast cancer is the most common cancer type amongst women in the United States and will account for approximately 7% of all cancer-related deaths each year. For most breast cancer patients, conventional genotoxic therapy is the standard of the care. Unfortunately, as breast cancer progresses it becomes treatment resistant and incurable. Therefore, understanding mechanisms of treatment response and resistance are of paramount importance. Stromal communication with cancer cells is a major determinant of progression and treatment response. We show that stromal and breast cancer (BrCa) cells utilize paracrine and juxtacrine signaling to drive progression and conventional therapy resistance. Upon heterotypic interaction, exosomes are unidirectionally transferred from stromal to breast cancer cells. Breast cancer cells stimulate stromal cell upregulation of RNA polymerase III through activation of stromal NOTCH1 and MYC. This results in a subsequent increase in stromal 5’triphosphate RN7SL1, an SRP RNA, in exosomes. Unlike cytoplasmic RN7SL1 that is shielded by RNA binding proteins (RBPs), RN7SL1 in exosomes produced after breast cancer cell interaction lack RBPs like SRP9 and SRP14. Consequently, unshielded stromal RN7SL1 in exosomes, which is also found in cancer patients, is transferred to breast cancer cells to stimulate the pattern recognition receptor RIG-I and activate STAT1-dependent anti-viral signaling. In parallel, stromal cells also activate NOTCH3 on breast cancer cells. The paracrine anti-viral and juxtacrine NOTCH3 pathways converge as STAT1 facilitates transcriptional responses to NOTCH3 and expands therapy resistant tumor-initiating cells. Primary human and mouse breast cancer analysis support the role of anti-viral and NOTCH3 pathway crosstalk in maximal activation of NOTCH signaling and stromal-mediated resistance. Stromal-mediated therapy resistance can be overcome by combination of conventional therapy with γ-secretase inhibitors. Thus, RBPs shield endogenous POL3-driven RNA from RIG-I, a process circumvented when breast cancer cells coerce stromal cells to propagate anti-viral signaling through exosomes. Anti-viral and NOTCH3 signaling then converge to enhance tumor growth, metastasis, and therapy resistance

Exosomes in the tumor microenvironment as mediators of cancer therapy resistance

Abstract Exosomes are small extracellular vesicles that contain genetic material, proteins, and lipids. They function as potent signaling molecules between cancer cells and the surrounding cells that comprise the tumor microenvironment (TME). Exosomes derived from both tumor and stromal cells have been implicated in all stages of cancer progression and play an important role in therapy resistance. Moreover, due to their nature as mediators of cell-cell communication, they are integral to TME-dependent therapy resistance. In this review, we discuss current exosome isolation and profiling techniques and their role in TME interactions and therapy resistance. We also explore emerging clinical applications of both exosomes as biomarkers, direct therapeutic targets, and engineered nanocarriers. In order to fully understand the TME, careful interrogation of exosomes and their cargo is critical. This understanding is a promising avenue for the development of effective clinical applications

Exosome transfer from stromal to breast cancer cells regulates therapy resistance pathways

Stromal communication with cancer cells can influence treatment response. We show that stromal and breast cancer (BrCa) cells utilize paracrine and juxtacrine signaling to drive chemotherapy and radiation resistance. Upon heterotypic interaction, exosomes are transferred from stromal to BrCa cells. RNA within exosomes, which are largely noncoding transcripts and transposable elements, stimulates the pattern recognition receptor RIG-I to activate STAT1-dependent antiviral signaling. In parallel, stromal cells also activate NOTCH3 on BrCa cells. The paracrine antiviral and juxtacrine NOTCH3 pathways converge as STAT1 facilitates transcriptional responses to NOTCH3 and expands therapy-resistant tumor-initiating cells. Primary human and/or mouse BrCa analysis support the role of antiviral/NOTCH3 pathways in NOTCH signaling and stroma-mediated resistance, which is abrogated by combination therapy with gamma secretase inhibitors. Thus, stromal cells orchestrate an intricate crosstalk with BrCa cells by utilizing exosomes to instigate antiviral signaling. This expands BrCa subpopulations adept at resisting therapy and reinitiating tumor growth

Patterns of transcription factor programs and immune pathway activation define four major subtypes of SCLC with distinct therapeutic vulnerabilities.

Despite molecular and clinical heterogeneity, small cell lung cancer (SCLC) is treated as a single entity with predictably poor results. Using tumor expression data and non-negative matrix factorization, we identify four SCLC subtypes defined largely by differential expression of transcription factors ASCL1, NEUROD1, and POU2F3 or low expression of all three transcription factor signatures accompanied by an Inflamed gene signature (SCLC-A, N, P, and I, respectively). SCLC-I experiences the greatest benefit from the addition of immunotherapy to chemotherapy, while the other subtypes each have distinct vulnerabilities, including to inhibitors of PARP, Aurora kinases, or BCL-2. Cisplatin treatment of SCLC-A patient-derived xenografts induces intratumoral shifts toward SCLC-I, supporting subtype switching as a mechanism of acquired platinum resistance. We propose that matching baseline tumor subtype to therapy, as well as manipulating subtype switching on therapy, may enhance depth and duration of response for SCLC patients

KEAP1/NFE2L2 Mutations Predict Lung Cancer Radiation Resistance That Can Be Targeted by Glutaminase Inhibition.

Tumor genotyping is not routinely performed in localized non-small cell lung cancer (NSCLC) due to lack of associations of mutations with outcome. Here, we analyze 232 consecutive patients with localized NSCLC and demonstrate that KEAP1 and NFE2L2 mutations are predictive of high rates of local recurrence (LR) after radiotherapy but not surgery. Half of LRs occurred in tumors with KEAP1/NFE2L2 mutations, indicating that they are major molecular drivers of clinical radioresistance. Next, we functionally evaluate KEAP1/NFE2L2 mutations in our radiotherapy cohort and demonstrate that only pathogenic mutations are associated with radioresistance. Furthermore, expression of NFE2L2 target genes does not predict LR, underscoring the utility of tumor genotyping. Finally, we show that glutaminase inhibition preferentially radiosensitizes KEAP1-mutant cells via depletion of glutathione and increased radiation-induced DNA damage. Our findings suggest that genotyping for KEAP1/NFE2L2 mutations could facilitate treatment personalization and provide a potential strategy for overcoming radioresistance conferred by these mutations. SIGNIFICANCE: This study shows that mutations in KEAP1 and NFE2L2 predict for LR after radiotherapy but not surgery in patients with NSCLC. Approximately half of all LRs are associated with these mutations and glutaminase inhibition may allow personalized radiosensitization of KEAP1/NFE2L2-mutant tumors.This article is highlighted in the In This Issue feature, p. 1775