Triple-negative (ER-, HER2-, PR-) breast cancer (TNBC) is an aggressive disease with a poor prognosis with no available molecularly targeted therapy. Silencing of micRoRNA-145 (miR-145) may be a defining marker of TNBC based on molecular profiling and deep sequencing. Therefore, the molecular mechanism behind miR-145 down-regulation in TNBC was examined. Overexpression of the long non-coding RNA, lincRNA-RoR, functions as a competitive endogenous RNA sponge in TNBC. Interestingly, lincRNA-RoR is dramatically upregulated in TNBC and in metastatic disease and knockdown restores miR-145 expression. Previous reports suggest that miR-145 has growth suppressive activity in some breast cancers; however, the current data in TNBC indicates that miR-145 does not impact proliferation or apoptosis but instead, miR-145 regulates tumor cell invasion. Investigation of miR-145 regulated pathways involved in tumor invasion revealed a novel target, the small GTPase ADP-ribosylation factor 6 (Arf6). Subsequent analysis demonstrated that ARF6, a known regulator of breast tumor cell invasion, is dramatically upregulated in TNBC and in breast tumor metastasis. Mechanistically, ARF6 regulates E-cadherin localization and impacts cell-cell adhesion. These results reveal a lincRNA-RoR/miR-145/ARF6 pathway that regulates invasion in TNBCs. Implications The lincRNA-RoR/miR-145/ARF6 pathway is critical to TNBC metastasis and could serve as biomarkers or therapeutic targets for improving survival.

The tumor microenvironment plays a critical role in regulating breast tumor progression. Signaling between preadipocytes and breast cancer cells has been found to promote breast tumor formation and metastasis. Exosomes secreted from preadipocytes are important components of the cancer stem cell niche. Mouse preadipocytes (3T3L1) are treated with the natural antitumor compound shikonin (SK) and exosomes derived from mouse preadipocytes are co-cultured with MCF10DCIS cells. We examine how preadipocyte-derived exosomes can regulate early-stage breast cancer via regulating stem cell renewal, cell migration, and tumor formation. We identify a critical miR-140/SOX2/SOX9 axis that regulates differentiation, stemness, and migration in the tumor microenvironment. Next, we find that the natural antitumor compound SK can inhibit preadipocyte signaling inhibiting nearby ductal carcinoma in situ (DCIS) cells. Through co-culture experiments, we find that SK-treated preadipocytes secrete exosomes with high levels of miR-140, which can impact nearby DCIS cells through targeting SOX9 signaling. Finally, we find that preadipocyte-derived exosomes promote tumorigenesis in vivo, providing strong support for the importance of exosomal signaling in the tumor microenvironment. Our data also show that targeting the tumor microenvironment may assist in blocking tumor progression.

More than 40% of the U.S. population are clinically obese and suffer from metabolic syndrome with an increased risk of postmenopausal estrogen receptor-positive breast cancer. Adipocytes are the primary component of adipose tissue and are formed through adipogenesis from precursor mesenchymal stem cells. While the major molecular pathways of adipogenesis are understood, little is known about the noncoding RNA signaling networks involved in adipogenesis. Using adipocyte-derived stem cells (ADSCs) isolated from wild-type and microRNA 140 (miR-140) knockout mice, we identify a novel miR-140/long noncoding RNA (lncRNA) NEAT1 signaling network necessary for adipogenesis. miR-140 knockout ADSCs have dramatically decreased adipogenic capabilities associated with downregulation of NEAT1 expression. We identified a miR-140 binding site in NEAT1 and found that mature miR-140 in the nucleus can physically interact with NEAT1, leading to increased NEAT1 expression. We demonstrated that reexpression of NEAT1 in miR-140 knockout ADSCs is sufficient to restore their ability to undergo differentiation. Our results reveal an exciting new noncoding RNA signaling network that regulates adipogenesis and that is a potential new target in the prevention or treatment of obesity. More than 40% of American adults are overweight or obese, and there are over 40 million obese women in America (1). Obese and overweight women are at greater risk for postmenopausal breast cancer and have dramatically higher rates of cancer recurrence and mortality (2, 3). Obesity is characterized by metabolic imbalance leading to adipocyte hypertrophy and hyperplasia and the excess accumulation of adipose tissue. During adipogenesis, mesenchymal stem cells (MSC) commit to the adipogenic lineage, forming proliferative, MSC-like cells called preadipocytes. By differentiating into mature adipocytes, preadipocytes replenish the nonproliferative mature adipocytes that are the bulk of white adipose tissue (4). Mature adipocytes secrete hormones and adipokines that, in addition to their metabolic function, promote breast tumor aggressiveness and invasion (5). Deciphering the mechanisms of preadipocyte differentiation and adipocyte-breast cancer cell interaction will greatly further our understanding of and our ability to treat breast cancers.MicroRNAs (miRNAs) are essential regulators of cellular function and gene expression. After nuclear processing, miRNA precursors are exported to the cytoplasm, where the mature miRNA is formed. miRNAs associate with the RNA-induced silencing complex (RISC) and base pair to seed sequences in the 3= untranslated region (UTR) of target mRNAs. This guides the RISC to the mRNA, causing degradation or inhibition of translation. miRNAs primarily function in the cytoplasm; however, some have been shown to translocate back into the nucleus and degrade nuclear RNA molecules (6). Nuclear miRNAs have also been shown to mediate mRNA upregulation by RNA activation (RNAa).

Dysregulation of long non-codng RNA (lncRNA) expression has been found to contribute to tumorigenesis. However, the roles of lncRNAs in BRCA1-related breast cancer remain largely unknown. In this study, we delineate the role of the novel BRCA1/lncRNA NEAT1 signaling axis in breast tumorigenesis. BRCA1 inhibits NEAT1 expression potentially through binding to its genomic binding site upstream of the NEAT1 gene. BRCA1 deficiency in human normal/cancerous breast cells and mouse mammary glands leads to NEAT1 overexpression. Our studies show that NEAT1 upregulation resulting from BRCA1 deficiency stimulates in vitro and in vivo breast tumorigenicity. We have further identified molecular mediators downstream of the BRCA1/NEAT1 axis. NEAT1 epigenetically silences miR-129-5p expression by promoting the DNA methylation of the CpG island in the miR-129 gene. Silencing of miR-129-5p expression by NEAT1 results in upregulation of WNT4 expression, a target of miR-129-5p, which leads to activation of oncogenic WNT signaling. Our functional studies indicate that this NEAT1/miR-129-5p/WNT4 axis contributes to the tumorigenic effects of BRCA1 deficiency. Finally our in silico expression correlation analysis suggests the existence of the BRCA1/NEAT1/miR-129-5p axis in breast cancer. Our findings, taken together, suggest that the dysregulation of the BRCA1/NEAT1/miR-129-5p/WNT4 signaling axis is involved in promoting breast tumorigenesis.

Cancer treatment has rapidly entered the age of immunotherapy, and it is becoming clear that the effective therapy of established tumors necessitates rational multi-combination immunotherapy strategies. But even in the advent of immunotherapy, the clinical role of standard-of-care chemotherapy regimens still remains significant and may be complementary to emerging immunotherapeutic approaches. Depending on dose, schedule, and agent, chemotherapy can induce immunogenic cell death, resulting in the release of tumor antigens to stimulate an immune response, or immunogenic modulation, sensitizing surviving tumor cells to immune cell killing. While these have been previously defined as distinct processes, in this review we examine the published mechanisms supporting both immunogenic cell death and immunogenic modulation and propose they be reclassified as similar effects termed “immunogenic cell stress.”Treatment-induced immunogenic cell stress is an important result of cytotoxic chemotherapy and future research should consider immunogenic cell stress as a whole rather than just immunogenic cell death or immunogenic modulation. Cancer treatment strategies should be designed specifically to take advantage of these effects in combination immunotherapy, and novel chemotherapy regimens should be designed and investigated to potentially induce all aspects of immunogenic cell stress.