Repurposing of drugs as STAT3 inhibitors for cancer therapy.

Drug repurposing is a valuable approach in delivering new cancer therapeutics rapidly into the clinic. Existing safety and patient tolerability data for drugs already in clinical use represent an untapped resource in terms of identifying therapeutic agents for off-label protein targets. The multicellular effects of STAT3 mediated by a range of various upstream signaling pathways make it an attractive therapeutic target with utility in a range of diseases including cancer, and has led to the development of a variety of STAT3 inhibitors. Moreover, heightened STAT3 transcriptional activation in tumor cells and within the cells of the tumor microenvironment contribute to disease progression. Consequently, there are many STAT3 inhibitors in preclinical development or under evaluation in clinical trials for their therapeutic efficacy predominantly in inflammatory diseases and cancer. Despite these advances, many challenges remain in ultimately providing STAT3 inhibitors to patients as cancer treatments, highlighting the need not only for a better understanding of the mechanisms associated with STAT3 activation, but also how various pharmaceutical agents suppress STAT3 activity in various cancers. In this review we discuss the importance of STAT3-dependent functions in cancer, review the status of compounds designed as direct-acting STAT3 inhibitors, and describe some of the strategies for repurposing of drugs as STAT3 inhibitors for cancer therapy.

Therapeutic Targeting of the Tumour Microenvironment in Metastatic Colorectal Cancer.

Liver metastasis is the primary contributor to the death of patients with colorectal cancer. Despite the overall success of current treatments including targeted therapy, chemotherapy, and immunotherapy combinations in colorectal cancer patients, the prognosis of patients with liver metastasis remains poor. Recent studies have highlighted the importance of the tumour microenvironment and the crosstalk within that determines the fate of circulating tumour cells in distant organs. Understanding the interactions between liver resident cells and tumour cells colonising the liver opens new therapeutic windows for the successful treatment of metastatic colorectal cancer. Here we discuss critical cellular interactions within the tumour microenvironment in primary tumours and in liver metastases that highlight potential therapeutic targets. We also discuss recent therapeutic advances for the treatment of metastatic colorectal cancer.

Comparing the effectiveness of general dietary advice versus a very low energy diet in an obese outpatient population in Australia.

PURPOSE: Obesity is a major public health burden. Outpatient clinics are an essential resource for individuals with obesity to access advice for weight loss management. The aim of this study was to compare anthropometric and weight loss outcomes between participants receiving general dietary (GD) advice, and those on a very low energy diet (VLED) under non-trial conditions. METHODS: Data from 276 adults with obesity attending a multidisciplinary weight management clinic were analysed. Changes in anthropometry, body composition, and blood pressure (BP) over 12 months were analysed using linear mixed-effects models. RESULTS: Males on the GD demonstrated statistically greater reductions in body weight (BW), BMI, percent fat mass (FM), systolic BP, waist and hip circumference (p < 0.01). Changes in males on a VLED did not reach significance. Females showed statistically significant reductions in BW, BMI, waist and hip circumference regardless of dietary intervention (p < 0.01); those on the GD significantly reduced percent FM (p < 0.001). Females on a VLED had statistically greater reductions in BW, BMI and systolic BP compared to those on the GD. No effect of exercise physiologist was observed in this study. Participants prescribed a GD attended for significantly longer than those on a VLED (p < 0.05), irrespective of gender. At 12 months, 14.3 and 4.5% of males and females on a VLED were still attending, compared to 10.6 and 4.5% on the GD. CONCLUSIONS: In this retrospective study, females in both dietary intervention groups achieved significant changes across multiple measures. Only men receiving GD advice demonstrated significant changes. LEVEL OF EVIDENCE: Level II-2.

DCLK1 induces a pro-tumorigenic phenotype to drive gastric cancer progression.

Doublecortin-like kinase 1 (DCLK1) is a proposed driver of gastric cancer (GC) that phosphorylates serine and threonine residues. Here, we showed that the kinase activity of DCLK1 orchestrated cancer cell-intrinsic and-extrinsic processes that led to pro-invasive and pro-metastatic reprogramming of GC cells. Inhibition of the kinase activity of DCLK1 reduced the growth of subcutaneous xenograft tumors formed from MKN1 human gastric carcinoma cells in mice and decreased the abundance of the stromal markers α-Sma, vimentin, and collagen. Similar effects were seen in mice with xenograft tumors formed from MKN1 cells expressing a kinase-inactive DCLK1 mutant (MKN1D511N). MKN1D511N cells also had reduced in vitro migratory potential and stemness compared with control cells. Mice orthotopically grafted with MKN1 cells overexpressing DCLK1 (MKN1DCLK1) showed increased invasiveness and had a greater incidence of lung metastases compared with those grafted with control MKN1 cells. Mechanistically, we showed that the chemokine CXCL12 acted downstream of DCLK1 in cultured MKN1 cells and in mice subcutaneously implanted with gastric tumors formed by MKN1DCLK1 cells. Moreover, inhibition of the kinase activity of DCLK1 or the expression of DCLK1D511N reversed the pro-tumorigenic and pro-metastatic phenotype. Together, this study establishes DCLK1 as a broadly acting and potentially targetable promoter of GC.

Mechanisms of cellular crosstalk in the gastric tumor microenvironment are mediated by YAP1 and STAT3.

Deregulation of the Hippo pathway is a driver for cancer progression and treatment resistance. In the context of gastric cancer, YAP1 is a biomarker for poor patient prognosis. Although genomic tumor profiling provides information of Hippo pathway activation, the present study demonstrates that inhibition of Yap1 activity has anti-tumor effects in gastric tumors driven by oncogenic mutations and inflammatory cytokines. We show that Yap1 is a key regulator of cell metabolism, proliferation, and immune responses in normal and neoplastic gastric epithelium. We propose that the Hippo pathway is targetable across gastric cancer subtypes and its therapeutic benefits are likely to be mediated by both cancer cell-intrinsic and -extrinsic mechanisms.

Combination of bazedoxifene with chemotherapy and SMAC-mimetics for the treatment of colorectal cancer.

Excessive STAT3 signalling via gp130, the shared receptor subunit for IL-6 and IL-11, contributes to disease progression and poor survival outcomes in patients with colorectal cancer. Here, we provide evidence that bazedoxifene inhibits tumour growth via direct interaction with the gp130 receptor to suppress IL-6 and IL-11-mediated STAT3 signalling. Additionally, bazedoxifene combined with chemotherapy synergistically reduced cell proliferation and induced apoptosis in patient-derived colon cancer organoids. We elucidated that the primary mechanism of anti-tumour activity conferred by bazedoxifene treatment occurs via pro-apoptotic responses in tumour cells. Co-treatment with bazedoxifene and the SMAC-mimetics, LCL161 or Birinapant, that target the IAP family of proteins, demonstrated increased apoptosis and reduced proliferation in colorectal cancer cells. Our findings provide evidence that bazedoxifene treatment could be combined with SMAC-mimetics and chemotherapy to enhance tumour cell apoptosis in colorectal cancer, where gp130 receptor signalling promotes tumour growth and progression.

Ehf controls mammary alveolar lineage differentiation and is a putative suppressor of breast tumorigenesis.

The transcription factor EHF is highly expressed in the lactating mammary gland, but its role in mammary development and tumorigenesis is not fully understood. Utilizing a mouse model of Ehf deletion, herein, we demonstrate that loss of Ehf impairs mammary lobuloalveolar differentiation at late pregnancy, indicated by significantly reduced levels of milk genes and milk lipids, fewer differentiated alveolar cells, and an accumulation of alveolar progenitor cells. Further, deletion of Ehf increased proliferative capacity and attenuated prolactin-induced alveolar differentiation in mammary organoids. Ehf deletion also increased tumor incidence in the MMTV-PyMT mammary tumor model and increased the proliferative capacity of mammary tumor organoids, while low EHF expression was associated with higher tumor grade and poorer outcome in luminal A and basal human breast cancers. Collectively, these findings establish EHF as a non-redundant regulator of mammary alveolar differentiation and a putative suppressor of mammary tumorigenesis.

Oestradiol reduces liver receptor homolog-1 mRNA transcript stability in breast cancer cell lines.

The expression of orphan nuclear receptor Liver Receptor Homolog-1 (LRH-1) is elevated in breast cancer and promotes proliferation, migration and invasion in vitro. LRH-1 expression is regulated by oestrogen (E2), with LRH-1 mRNA transcript levels higher in oestrogen receptor α (ERα) positive (ER+) breast cancer cells compared to ER- cells. However, the presence of LRH-1 protein in ER- cells suggests discordance between mRNA transcript levels and protein expression. To understand this, we investigated the impact of mRNA and protein stability in determining LRH-1 protein levels in breast cancer cells. LRH-1 transcript levels were significantly higher in ER+ versus ER- breast cancer cells lines; however LRH-1 protein was expressed at similar levels. We found LRH-1 mRNA and protein was more stable in ER- compared to ER+ cell lines. The tumor-specific LRH-1 variant isoform, LRH-1v4, which is highly responsive to E2, showed increased mRNA stability in ER- versus ER+ cells. In addition, in MCF-7 and T47-D cell lines, LRH-1 total mRNA stability was reduced with E2 treatment, this effect mediated by ERα. Our data demonstrates that in ER- cells, increased mRNA and protein stability contribute to the abundant protein expression levels. Expression and immunolocalisation of LRH-1 in ER- cells as well as ER- tumors suggests a possible role in the development of ER- tumors. The modulation of LRH-1 bioactivity may therefore be beneficial as a treatment option in both ER- and ER+ breast cancer.

Distinct nuclear receptor expression in stroma adjacent to breast tumors.

The interaction between breast tumor epithelial and stromal cells is vital for initial and recurrent tumor growth. While breast cancer-associated stromal cells provide a favorable environment for proliferation and metastasis, the molecular mechanisms contributing to this process are not fully understood. Nuclear receptors (NRs) are intracellular transcription factors that directly regulate gene expression. Little is known about the status of NRs in cancer-associated stroma. Nuclear Receptor Low-Density Taqman Arrays were used to compare the gene expression profiles of all 48 NR family members in a collection of primary cultured cancer-associated fibroblasts (CAFs) obtained from estrogen receptor (ER)α positive breast cancers (n = 9) and normal breast adipose fibroblasts (NAFs) (n = 7). Thirty-three of 48 NRs were expressed in both the groups, while 11 NRs were not detected in either. Three NRs (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 (DAX-1); estrogen-related receptor beta (ERR-ß); and RAR-related orphan receptor beta (ROR-ß)) were only detected in NAFs, while one NR (liver receptor homolog-1 (LRH-1)) was unique to CAFs. Of the NRs co-expressed, four were significantly down-regulated in CAFs compared with NAFs (RAR-related orphan receptor-α (ROR-α); Thyroid hormone receptor-ß (TR-ß); vitamin D receptor (VDR); and peroxisome proliferator-activated receptor-γ (PPAR-γ)). Quantitative immunohistochemistry for LRH-1, TR-ß, and PPAR-γ proteins in stromal fibroblasts from an independent panel of breast cancers (ER-positive (n = 15), ER-negative (n = 15), normal (n = 14)) positively correlated with mRNA expression profiles. The differentially expressed NRs identified in tumor stroma are key mediators in aromatase regulation and subsequent estrogen production. Our findings reveal a distinct pattern of NR expression that therefore fits with a sustained and increased local estrogen microenvironment in ER-positive tumors. NRs in CAFs may provide a new avenue for the development of intratumoral-targeted therapies in breast cancer.

STAT3 Signaling in Breast Cancer: Multicellular Actions and Therapeutic Potential.

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.