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Natural killer (NK) cells are cytotoxic lymphocytes that accumulate within the tumor microenvironment and are generally considered to be antitumorigenic. Using single-cell RNA sequencing and functional analysis of multiple triple-negative breast cancer (TNBC) and basal tumor samples, we observed a unique subcluster of Socs3 high CD11b − CD27 − immature NK cells that were present only in TNBC samples. These tumor-infiltrating NK cells expressed a reduced cytotoxic granzyme signature and, in mice, were responsible for activating cancer stem cells through Wnt signaling. NK cell–mediated activation of these cancer stem cells subsequently enhanced tumor progression in mice, whereas depletion of NK cells or Wnt ligand secretion from NK cells by LGK-974 decreased tumor progression. In addition, NK cell depletion or inhibition of their function improved anti–programmed cell death ligand 1 (PD-L1) antibody or chemotherapy response in mice with TNBC. Furthermore, tumor samples from patients with TNBC and non-TNBC revealed that increased numbers of CD56 bright NK cells were present in TNBC tumors and were correlated to poor overall survival in patients with TNBC. Together, our findings identify a population of protumorigenic NK cells that may be exploited for both diagnostic and therapeutic strategies to improve outcomes for patients with TNBC.

Development of chemoresistance in breast cancer patients greatly increases mortality. Thus, understanding mechanisms underlying breast cancer resistance to chemotherapy is of paramount importance to overcome this clinical challenge. Although activated Notch receptors have been associated with chemoresistance in cancer, the specific Notch ligands and their molecular mechanisms leading to chemoresistance in breast cancer remain elusive. Using conditional knockout and reporter mouse models, we demonstrate that tumor cells expressing the Notch ligand Dll1 is important for tumor growth and metastasis and bear similarities to tumor-initiating cancer cells (TICs) in breast cancer. RNA-seq and ATAC-seq using reporter models and patient data demonstrated that NF-κB activation is downstream of Dll1 and is associated with a chemoresistant phenotype. Finally, pharmacological blocking of Dll1 or NF-κB pathway completely sensitizes Dll1+ tumors to chemotherapy, highlighting therapeutic avenues for chemotherapy resistant breast cancer patients in the near future., Although activated Notch receptors have been associated with chemoresistance in cancer, the role of specific Notch ligands remain elusive. Here, the authors show that in breast cells the Notch ligand DLL1 is expressed in cells with a cancer stem cell phenotype and promote doxorubicin resistance in part through NF-kB, as well as metastasis.

Triple-negative breast cancer (TNBC) is characterized by a high degree of immune infiltrate in the tumour microenvironment, which may influence the fate of TNBC cells. We reveal that loss of the tumour suppressive transcription factor Elf5 in TNBC cells activates intrinsic interferon-γ (IFN-γ) signalling, promoting tumour progression and metastasis. Mechanistically, we find that loss of the Elf5-regulated ubiquitin ligase FBXW7 ensures stabilization of its putative protein substrate IFN-γ receptor 1 (IFNGR1) at the protein level in TNBC. Elf5(low) tumours show enhanced IFN-γ signalling accompanied by an increase of immunosuppressive neutrophils within the tumour microenvironment and increased programmed death ligand 1 expression. Inactivation of either programmed death ligand 1 or IFNGR1 elicited a robust anti-tumour and/or anti-metastatic effect. A positive correlation between ELF5 and FBXW7 expression and a negative correlation between ELF5, FBXW7 and IFNGR1 expression in the tumours of patients with TNBC strongly suggest that this signalling axis could be exploited for patient stratification and immunotherapeutic treatment strategies for Elf5(low) patients with TNBC.

Elf5 is a transcription factor known to regulate critical developmental processes and has been shown to act as a tumour suppressor in multiple cancers. Elf5 knockout mice are embryonically lethal, limiting in vivo studies pertaining to its function. Moreover, haploinsufficiency of Elf5 limits the use of current mouse models to investigate adult tissue distribution of Elf5. Here, we successfully generated Elf5Cre ERT 2- GFP bacterial artificial chromosome (BAC) transgenic mice and show that Elf5+ cells are present in several adult tissues, where its expression was previously not known. Our study demonstrates the unique distribution of Elf5+ cells in multiple adult organs, which will facilitate future studies investigating the function of Elf5 in these tissues during homeostasis, repair and cancer.

Altered glucose uptake and metabolism is the key characteristic of cancer cells including hepatocellular carcinoma (HCC). However, role of glucose availability in chemotherapeutic outcome of HCC is unclear. The present study investigates the effect of glucose facilitated sensitization of HCC cells towards doxorubicin (DOX) and sorafenib (SORA). In HCC cells, we observed that hyperglycemic culture condition (HG) is associated with increased sensitivity towards DOX and SORA. P-glycoprotein (P-gp), a transporter involved in drug efflux, was elevated in HCC cells in NG, rendering them less susceptible to DOX and SORA. Further, this study demonstrated that knockdown of dickkopf protein 4 (DKK4), a Wnt antagonist protein, causes enhanced glucose uptake and reduction in P-gp level rendering HCC cells in NG sensitive to DOX and SORA. Moreover, HG elevates the level of intracellular reactive oxygen species (ROS), which regulates P-gp. Alteration in intracellular ROS did not directly affect regulation of DKK4 in HCC cells. Functional assays suggest that alterations in DKK4 and P-gp level in HCC cells are dependent on glucose availability and changes in ROS level because of enhanced glucose utilization, respectively. Collectively, the present study highlights direct involvement of glucose-induced ROS, DKK4 and P-gp in altering the sensitivity of HCC cells towards DOX and SORA.

Background Obesity is associated with increased risk, poor prognosis and outcome of therapy, in various cancers. Obesity-associated factors or adipokines, especially leptin and resistin, are purported to promote growth, survival, proliferation, and invasiveness of cancer cells. However, the mechanistic link between these adipokines and therapeutic response in malignancies is not clearly understood. Methods ob/ob and db/db mouse models were used in this study to evaluate the role of leptin and resistin towards the outcome of dacarbazine (DTIC) therapy in melanoma. Unique in vitro approaches were employed to complement in vivo findings by culturing melanoma cells in the serum collected from the experimental mice. Results Here, we have shown the role of important adipokines leptin and resistin in growth and the outcome of DTIC therapy in melanoma. Both leptin and resistin not only enhance proliferation of melanoma cells but also are involved in impairing the therapeutic efficacy of DTIC. Leptin and resistin treatment caused an increase in the protein levels of fatty acid synthase (FASN) and caveolin 1 (Cav-1) respectively, through their stabilization in A375 cells. Further, it was observed that leptin and resistin impaired the response of melanoma cells to DTIC via upregulation of heat shock protein 90 (Hsp90) and P-glycoprotein (P-gp) respectively. Conclusion These findings unraveled the involvement of adipokines (leptin and resistin) in melanoma progression, and more importantly, in the outcome of DTIC therapy. Electronic supplementary material The online version of this article (10.1186/s40170-018-0176-5) contains supplementary material, which is available to authorized users.

Resistin, a proinflammatory cytokine, is elevated in a number of pathological disorders, including cancer. The serum resistin level in colon cancer patients is elevated and correlates with tumor grade. However, the implications of increased resistin on colon cancer cells remain unclear. In the present study, we find that resistin binds to TLR4 on colon cancer cell membrane and initiates TLR4-MyD88-dependent activation of ERK. In addition, the upregulation of SOCS3 by ERK downregulates the JAK2/TAT3 pathway and causes the arrest of cells in G1 phase. Interestingly, we observe that resistin-exposed cells survive 5-fluorouracil treatment because of a decrease in drug uptake due to the arrest of cells in G1 phase.

Epithelial-to-mesenchymal transition (EMT) is a process through which epithelial cells lose their epithelial characteristics and cell–cell contact, thus increasing their invasive potential. In addition to its well-known roles in embryonic development, wound healing, and regeneration, EMT plays an important role in tumor progression and metastatic invasion. In breast cancer, EMT both increases the migratory capacity and invasive potential of tumor cells, and initiates protumorigenic alterations in the tumor microenvironment (TME). In particular, recent evidence has linked increased expression of EMT markers such as TWIST1 and MMPs in breast tumors with increased immune infiltration in the TME. These immune cells then provide cues that promote immune evasion by tumor cells, which is associated with enhanced tumor progression and metastasis. In the current review, we will summarize the current knowledge of the role of EMT in the biology of different subtypes of breast cancer. We will further explore the correlation between genetic switches leading to EMT and EMT-induced alterations within the TME that drive tumor growth and metastasis, as well as their possible effect on therapeutic response in breast cancer.

Epidemiological studies over the last few decades have shown a strong influence of obesity on colon cancer risk and its progression. These studies have primarily focussed on the role of adipokines in driving cancer progression. We investigated the incidence of cancerous polyp formation and tumor progression in presence and absence of functional leptin along with exploring the role of tumor necrosis factor α (TNFα), under obese condition. By utilizing diet induced obese and genetically obese mice, carcinogen induced colon polyp formation was investigated. Experiments were performed using tumor tissues and cell lines to delineate the inter-relationship between leptin and TNFα. Data shown in this report indicates that in leptin knockdown obese mice, AOM/DSS induced polyps are smaller and lesser in numbers as compared to AOM/DSS induced polyps in diet induced obese mice. Further in vitro experiments suggest that abrogation of leptin associated pathways promote TNFα induced apoptosis. Mechanistically, we report that TNFα induces p53 independent cell death through up regulation of p53 upregulated modulator of apoptosis (PUMA). TNFα induced PUMA was inhibited upon pre- exposure of cells to leptin, prior to TNFα treatment. Collectively these results indicate that obesity due to leptin non-functionality facilitates TNFα induced colon cancer cell death.

Elf5 is a transcription factor known to regulate critical developmental processes and has been shown to act as a tumor suppressor in multiple cancers. Elf5 knockout mice are embryonically lethal, limiting in vivo studies pertaining to its function. Moreover, haploinsufficiency of Elf5 limits the use of current mouse models to investigate adult tissue distribution of Elf5. Here, we successfully generated Elf5(CreERT2-GFP) bacterial artificial chromosome (BAC) transgenic mice and show that Elf5(+) cells are present in several adult tissues, where its expression was previously not known. Our study demonstrates the unique distribution of Elf5(+) cells in multiple adult organs, which will facilitate future studies investigating the function of Elf5 in these tissues during homeostasis, repair, and cancer.

Background PCSK9 regulates low-density lipoprotein cholesterol (LDLc) level and has been implicated in hypercholesterolemia. Aberrant plasma lipid profile is often associated with various cancers. Clinically, the relationship between altered serum lipid level and hepatocellular carcinoma (HCC) has been documented; however, the underlying cause and implications of such dyslipidemia remain unclear. Methods The present study includes the use of HepG2 tumor xenograft model to study the potential role of glucose (by providing 15% glucose via drinking water) in regulating PCSK9 expression and associated hypercholesterolemia. To support in vivo findings, in vitro approaches were used by incubating HCC cells in culture medium with different glucose concentrations or treating the cells with glucose uptake inhibitors. Impact of hypercholesterolemia on chemotherapy was demonstrated by exogenously providing LDLc followed by appropriate in vitro assays. Results We observed that serum and hepatic PCSK9 level is decreased in mice which were provided with glucose containing water. Interestingly, serum and tumor PCSK9 level was upregulated in HepG2-tumor-bearing mice having access to water containing glucose. Additionally, elevated LDLc is detected in sera of these mice. In vitro studies indicated that PCSK9 expression was increased by high glucose availability with potential involvement of reactive oxygen species (ROS) and sterol regulatory element binding protein-1 (SREBP-1). Furthermore, it is also demonstrated that pre-treatment of cells with LDLc diminishes cytotoxicity of sorafenib in HCC cells. Conclusion Taken together, these results suggest a regulation of PCSK9 by high glucose which could contribute, at least partly, towards understanding the cause of hypercholesterolemia in HCC and its accompanied upshots in terms of altered response of HCC cells towards cancer therapy. Electronic supplementary material The online version of this article (10.1186/s40170-018-0187-2) contains supplementary material, which is available to authorized users.

Figure S1. Validation of immunodepletion of leptin form serum collected from HFD C57BL/6J mice. Figure S2. A375 cells were cultured in the presence of leptin or resistin along with inhibitors for 48Â h. Table S1. Evaluation of obesity-associated factors in WT and db/db mice. Table S2. Evaluation of obesity-associated factors in WT and db/db mice. (DOC 319 kb)

Figure S6. Screening of sorafenib and LDLc concentration (DOCX 76 kb)

Figure S2. Glucose specificity of PCSK9 regulation (DOCX 114 kb)

Figure S3. Effect of glucose on SREBP-1 and SREBP-2 (DOCX 50 kb)

Figure S5. Effect of glucose and PCSK9 overexpression on LDLR (DOCX 118 kb)

Figure S7. Effect of LDLc on sorafenib mediated signaling (DOCX 112 kb)

Figure S1. Effect of glucose feeding on serum insulin and hepatic LDLR levels. (DOCX 120 kb)

Table S1. Primer pair sets (DOCX 13 kb)

Figure S4. Effect of catalase on ROS generation in HG (DOCX 21 kb)

The tumour suppressor gene p53 is mutated in approximately 50% of the human cancers. p53 is involved in genotoxic stress-induced cellular responses. The role of EGFR and ERK in DNA-damage-induced apoptosis is well known. We investigated the involvement of activation of ERK signalling as a consequence of non-functional p53, in sensitivity of cells to doxorubicin. We performed cell survival assays in cancer cell lines with varying p53 status: MCF-7 (wild-type p53, WTp53), MDA MB-468 (mutant p53, MUTp53), H1299 (absence of p53, NULLp53) and an isogenic cell line MCF-7As (WTp53 abrogated). Our results indicate that enhanced chemosensitivity of cells lacking wild-type p53 function is because of elevated levels of EGFR which activates ERK. Additionally, we noted that independent of p53 status, pERK contributes to doxorubicin-induced cell death.

Elevated glycemic index, an important feature of diabetes is implicated in an increased risk of hepatocellular carcinoma (HCC). However, the underlying molecular mechanisms of this association are relatively less explored. Present study investigates the effect of hyperglycemia over HCC proliferation. We observed that high glucose culture condition (HG) specifically activates canonical Wnt signaling in HCC cells, which is mediated by suppression of DKK4 (a Wnt antagonist) expression and enhanced β-catenin level. Functional assays demonstrated that a normoglycemic culture condition (NG) maintains constitutive expression of DKK4, which controls HCC proliferation rate by suppressing canonical Wnt signaling pathway. HG diminishes DKK4 expression leading to loss of check at G0/G1/S phases of the cell cycle thereby enhancing HCC proliferation, in a β-catenin dependent manner. Interestingly, in NOD/SCID mice supplemented with high glucose, HepG2 xenografted tumors grew rapidly in which elevated levels of β-catenin, c-Myc and decreased levels of DKK4 were detected. Knockdown of DKK4 by shRNA promotes proliferation of HCC cells in NG, which is suppressed by treating cells exogenously with recombinant DKK4 protein. Our in vitro and in vivo results indicate an important functional role of DKK4 in glucose facilitated HCC proliferation.