A Selective ß-Catenin-Metadherin/CEACAM1-CCL3 Axis Mediates Metastatic Heterogeneity upon Tumor-Macrophage Interaction.

Tumor heterogeneity plays a key role in cancer relapse and metastasis, however, the distinct cellular behaviors and kinetics of interactions among different cancer cell subclones and the tumor microenvironment are poorly understood. By profiling an isogenic model that resembles spontaneous human ovarian cancer metastasis with an highly metastatic (HM) and non-metastatic (NM) tumor cell pair, one finds an upregulation of Wnt/ß-catenin signaling uniquely in HM. Using humanized immunocompetent mice, one shows for the first time that activated ß-catenin acts nonautonomously to modulate the immune microenvironment by enhancing infiltrating tumor-associated macrophages (TAM) at the metastatic site. Single-cell time-lapse microscopy further reveals that upon contact with macrophages, a significant subset of HM, but not NM, becomes polyploid, a phenotype pivotal for tumor aggressiveness and therapy resistance. Moreover, HM, but not NM, polarizes macrophages to a TAM phenotype. Mechanistically, ß-catenin upregulates cancer cell surface metadherin, which communicates through CEACAM1 expressed on macrophages to produce CCL3. Tumor xenografts in humanized mice and clinical patient samples both corroborate the relevance of enhanced metastasis, TAM activation, and polyploidy in vivo. The results thus suggest that targeting the ß-catenin-metadherin/CEACAM1-CCL3 positive feedback cascade holds great therapeutic potential to disrupt polyploidization of the cancer subclones that drive metastasis.

Experimental models for ovarian cancer research.

Among all gynecological malignancies, ovarian cancer (OC) accounts for the highest mortality rate due to high therapeutic resistance, prolonged latency and a lack of effective treatments. This calls for preclinical models that could recapitulate the histological, molecular and pathophysiological features of distinct OC subtypes. Various mouse models including tumor xenografts, genetically modified models, and novel 3D tumor models including organoids and organotypic co-culture models have been developed, and they serve as valuable assets to fulfill this demand. These models, particularly those patient-derived, can address the heterogeneity of OC and simulate OC progression in patients, hence bringing important insights for personalized treatments. In this review, we will discuss the merits and challenges of these models, and summarize their current preclinical applications in patient stratification and therapeutic research. Though limitations are inevitable, further optimization will render these models more clinically translatable in OC research.

p70 S6 kinase as a therapeutic target in cancers: More than just an mTOR effector.

p70 S6 kinase (p70S6K) is best known for its regulatory roles in protein synthesis and cell growth by phosphorylating its primary substrate, ribosomal protein S6, upon mitogen stimulation. The enhanced expression/activation of p70S6K has been correlated with poor prognosis in some cancer types, suggesting that it may serve as a biomarker for disease monitoring. p70S6K is a critical downstream effector of the oncogenic PI3K/Akt/mTOR pathway and its activation is tightly regulated by an ordered cascade of Ser/Thr phosphorylation events. Nonetheless, it should be noted that other upstream mechanisms regulating p70S6K at both the post-translational and post-transcriptional levels also exist. Activated p70S6K could promote various aspects of cancer progression such as epithelial-mesenchymal transition, cancer stemness and drug resistance. Importantly, novel evidence showing that p70S6K may also regulate different cellular components in the tumor microenvironment will be discussed. Therapeutic targeting of p70S6K alone or in combination with traditional chemotherapies or other microenvironmental-based drugs such as immunotherapy may represent promising approaches against cancers with aberrant p70S6K signaling. Currently, the only clinically available p70S6K inhibitors are rapamycin analogs (rapalogs) which target mTOR. However, there are emerging p70S6K-selective drugs which are going through active preclinical or clinical trial phases. Moreover, various screening strategies have been used for the discovery of novel p70S6K inhibitors, hence bringing new insights for p70S6K-targeted therapy.

Hypoxia-induced Nur77 activates PI3K/Akt signaling via suppression of Dicer/let-7i-5p to induce epithelial-to-mesenchymal transition.

Background: Colorectal cancer (CRC) and the associated metastatic lesions are reported to be hypoxic. Hypoxia is a common feature in the tumor microenvironment and a potent stimulant of CRC. We have identified a regulatory role of Nur77 on Akt activation to enhance ß-catenin signaling essential for CRC progression under hypoxic conditions. Methods: The functional role of Nur77 in hypoxia-induced EMT was examined by scattering assays to monitor the morphologies of CRC cell lines under 1% O2. Sphere formation assays were performed to investigate whether Nur77 induced cancer stem cell-like properties in hypoxic CRC cells. The expression of various epithelial-to-mesenchymal transition (EMT) and stemness markers was analyzed by qPCR and Western blotting. Finally, Nur77 function and signaling in vivo was ascertained in subcutaneous tumor xenograft or liver metastasis model in nude mice using CRC cells stably transfected with appropriate constructs. Results: Herein, we show, for the first time, that Nur77 is a novel regulator of microRNA biogenesis that may underlie its significant tumor-promoting activities in CRC cells under hypoxia. Mechanistically, Nur77 interacted with the tumor suppressor protein p63, leading to the inhibition of p63-dependent transcription of Dicer, an important miRNA processor and subsequent decrease in the biogenesis of let-7i-5p which targeted the 3'UTR of p110α mRNA and regulated its stability. Knockdown of Nur77 or overexpression of let-7i-5p inhibited the tumor metastasis in vivo. Conclusion: Our data uncovered a novel mechanistic link connecting Nur77, Akt, and invasive properties of CRC in the hypoxic microenvironment.

The Roles of GSK-3ß in Regulation of Retinoid Signaling and Sorafenib Treatment Response in Hepatocellular Carcinoma.

Rationale: Glycogen synthase kinase-3ß (GSK-3ß) plays key roles in metabolism and many cellular processes. It was recently demonstrated that overexpression of GSK-3ß can confer tumor growth. However, the expression and function of GSK-3ß in hepatocellular carcinoma (HCC) remain largely unexplored. This study is aimed at investigating the role and therapeutic target value of GSK-3ß in HCC. Methods: We firstly clarified the expression of GSK-3ß in human HCC samples. Given that deviated retinoid signalling is critical for HCC development, we studied whether GSK-3ß could be involved in the regulation. Since sorafenib is currently used to treat HCC, the involvement of GSK-3ß in sorafenib treatment response was determined. Co-immunoprecipitation, GST pull down, in vitro kinase assay, luciferase reporter and chromatin immunoprecipitation were used to explore the molecular mechanism. The biological readouts were examined with MTT, flow cytometry and animal experiments. Results: We demonstrated that GSK-3ß is highly expressed in HCC and associated with shorter overall survival (OS). Overexpression of GSK-3ß confers HCC cell colony formation and xenograft tumor growth. Tumor-associated GSK-3ß is correlated with reduced expression of retinoic acid receptor-ß (RARß), which is caused by GSK-3ß-mediated phosphorylation and heterodimerization abrogation of retinoid X receptor (RXRα) with RARα on RARß promoter. Overexpression of functional GSK-3ß impairs retinoid response and represses sorafenib anti-HCC effect. Inactivation of GSK-3ß by tideglusib can potentiate 9-cis-RA enhancement of sorafenib sensitivity (tumor inhibition from 48.3% to 93.4%). Efficient induction of RARß by tideglusib/9-cis-RA is required for enhanced therapeutic outcome of sorafenib, which effect is greatly inhibited by knocking down RARß. Conclusions: Our findings demonstrate that GSK-3ß is a disruptor of retinoid signalling and a new resistant factor of sorafenib in HCC. Targeting GSK-3ß may be a promising strategy for HCC treatment in clinic.

Substrates with patterned topography reveal metastasis of human cancer cells.

In this study, we aimed at studying the effects of engineered and patterned substrates on the migration characteristics of mammalian cancer cell lines. On the shallow topographical patterns, cells from different histological origins showed different migration speed and directionality. We also observed that cells from the same origin showed distinctive behaviour, suggesting these substrate topographies could distinguish cancer subtypes. To eliminate the influence of genetic background, we examined two isogenic subpopulations of ovarian cancer cell lines for their different metastatic activities. While these cell lines showed indistinguishable migration characteristics on a flat substrate, their motilities on the patterned substrates were highly different, suggesting that cancer cells' motilities on these substrates varied in a metastasis-dependent manner. While cells with different metastatic activities showed similar morphology and focal adhesion distribution on flat surface, vinculin aggregated into single cytoplasmic foci in metastatic cells cultured on the engineered substrates. This implies that the topographical patterns on the substrates induced vinculin redistribution in cancer cells with a higher invasive activity. The fabricated platforms with topographical patterns offer a novel in vitro technique for metastasis assessment. Moreover, such platforms could potentially provide the opportunity to sort cells in different metastatic states using advanced pattern designs and features.

Nur77: a potential therapeutic target in cancer.

INTRODUCTION: The orphan nuclear receptor Nur77 (also known as NR4A1, NGFIB, TR3, TIS1, NAK-1, or N10) is a unique transcription factor encoded by an immediate early gene. Nur77 signaling is deregulated in many cancers and constitutes an important molecule for drug targeting. AREAS COVERED: Nur77 as a versatile transcription factor that displays distinct dual roles in cell proliferation and apoptosis. In addition, several recent insights into Nur77's non-genomic signaling through its physical interactions with various signaling proteins and its phosphorylation-dependent regulation will be highlighted. The possible mechanisms by which Nur77 supports carcinogenesis and specific examples in different human cancers will be summarized. Different approaches to target Nur77 using mimetics, natural products, and synthetic compounds are also described. EXPERT OPINION: These latest findings shed light on the novel roles of Nur77 as an exploitable target for new cancer therapeutics. Further work which focuses on a more complete understanding of the Nur77 interactome as well as how the different networks of Nur77 functional interactions are orchestrated in a stimulus or context-specific way will aid the development of more selective, non-toxic approaches for targeting Nur77 in future.