Targeted siRNA nanotherapeutics against breast and ovarian metastatic cancer: a comprehensive review of the literature

Metastasis is considered the major cause of unsuccessful cancer therapy. The metastatic development requires tumor cells to leave their initial site, circulate in the blood stream, acclimate to new cellular environments at a remote secondary site and endure there. There are several steps in metastasis, including invasion, intravasation, circulation, extravasation, premetastatic niche formation, micrometastasis and metastatic colonization. siRNA therapeutics are appreciated for their usefulness in treatment of cancer metastasis. However, siRNA therapy as a single therapy may not be a sufficient option for control of metastasis. By combining siRNA with targeting, functional agents or small molecule drugs have shown potential effects that enhance therapeutic effectiveness. This review addresses multidrug resistance and metastasis in breast and ovarian cancers and highlights drug delivery strategies using siRNA therapeutics.

High Expression of CEMIP Correlates Poor Prognosis and the Tumur Microenvironment in Breast Cancer as a Promisingly Prognostic Biomarker

Cell migration-inducing hyaluronidase 1 (CEMIP), a Wnt-related protein and also known as KIAA1199, is implicated in the process of metastatic colonization in a variety of malignant tumors, including breast cancer (BC), which is one of the most frequently diagnosed tumors in women worldwide. In this study, multiple public databases, online analytical tools, and bioinformatics approaches were applied to explore the expression levels, regulatory mechanisms, and biological functions of CEMIP in BC. We illustrated that CEMIP was highly expressed in various kinds of carcinomas, including BC, especially advanced subtypes, and predicted less favorable prognosis (negatively associated with overall survival) in BC patients, which might be an independent prognostic factor. Then, we revealed that the mutation and high expression of CEMIP might lead to it as an oncogene. We also demonstrated that TP53 mutation, DNA hypo-methylation, and the expression changes of three potential upstream transcription factors (EZH2, EGR1, and JUN) of CEMIP were likely to cause the hyperexpression of CEMIP in BC. Moreover, our findings suggested that CEMIP might exert its carcinogenic roles in the tumor microenvironment via participation in the extracellular matrix formation, increasing cancer-associated fibroblast (CAF), M2 macrophage, and neutrophil infiltration and decreasing CD8+ T cell infiltration. In summary, our study provided more solid evidence for CEMIP as a prognostic and metastatic biomarker and a potential therapeutic target in BC. Of course, these findings also need more confirmations of basic experiments and further clinical trials in the future.

Novel temporal and spatial patterns of metastatic colonization from breast cancer rapid-autopsy tumor biopsies

Background Metastatic breast cancer is a deadly disease with a low 5-year survival rate. Tracking metastatic spread in living patients is difficult and thus poorly understood. Methods Via rapid autopsy, we have collected 30 tumor samples over 3 timepoints and across 8 organs from a triple-negative metastatic breast cancer patient. The large number of sites sampled, together with deep whole-genome sequencing and advanced computational analysis, allowed us to comprehensively reconstruct the tumor’s evolution at subclonal resolution. Results The most unique, previously unreported aspect of the tumor’s evolution that we observed in this patient was the presence of “subclone incubators,” defined as metastatic sites where substantial tumor evolution occurs before colonization of additional sites and organs by subclones that initially evolved at the incubator site. Overall, we identified four discrete waves of metastatic expansions, each of which resulted in a number of new, genetically similar metastasis sites that also enriched for particular organs (e.g., abdominal vs bone and brain). The lung played a critical role in facilitating metastatic spread in this patient: the lung was the first site of metastatic escape from the primary breast lesion, subclones at this site were likely the source of all four subsequent metastatic waves, and multiple sites in the lung acted as subclone incubators. Finally, functional annotation revealed that many known drivers or metastasis-promoting tumor mutations in this patient were shared by some, but not all metastatic sites, highlighting the need for more comprehensive surveys of a patient’s metastases for effective clinical intervention. Conclusions Our analysis revealed the presence of substantial tumor evolution at metastatic incubator sites in a patient, with potentially important clinical implications. Our study demonstrated that sampling of a large number of metastatic sites affords unprecedented detail for studying metastatic evolution.

A Zebrafish Model of Metastatic Colonization Pinpoints Cellular Mechanisms of Circulating Tumor Cell Extravasation

Metastasis is a multistep process in which cells must detach, migrate/invade local structures, intravasate, circulate, extravasate, and colonize. A full understanding of the complexity of this process has been limited by the lack of ability to study these steps in isolation with detailed molecular analyses. Leveraging a comparative oncology approach, we injected canine osteosarcoma cells into the circulation of transgenic zebrafish with fluorescent blood vessels in a biologically dynamic metastasis extravasation model. Circulating tumor cell clusters that successfully extravasated the vasculature as multicellular units were isolated under intravital imaging (n = 6). These extravasation-positive tumor cell clusters sublines were then molecularly profiled by RNA-Seq. Using a systems-level analysis, we pinpointed the downregulation of KRAS signaling, immune pathways, and extracellular matrix (ECM) organization as enriched in extravasated cells (p < 0.05). Within the extracellular matrix remodeling pathway, we identified versican (VCAN) as consistently upregulated and central to the ECM gene regulatory network (p < 0.05). Versican expression is prognostic for a poorer metastasis-free and overall survival in patients with osteosarcoma. Together, our results provide a novel experimental framework to study discrete steps in the metastatic process. Using this system, we identify the versican/ECM network dysregulation as a potential contributor to osteosarcoma circulating tumor cell metastasis.

Activation of epithelial-mesenchymal transition process during breast cancer progression – the impact of molecular subtype and stromal composition

Breast cancer (BC) is a heterogeneous disease with different molecular subtypes, which can be defined by oestrogen (ER), progesterone (PR) and human epidermal growth factor (HER2) receptors’ status as luminal, HER2+ and triple negative (TNBC). Molecular subtypes also differ in their epithelial-mesenchymal phenotype, which might be related to their aggressiveness, as activation of the epithelial-mesenchymal transition (EMT) is linked with increased ability of cancer cells to survive and metastasize. Nevertheless, the reverse process of mesenchymal-epithelial transition was shown to be required to sustain metastatic colonization. In this study we aimed to analyse activation of the EMT process in primary tumours (PT), which have (N+) or have not (N–) colonized the lymph nodes, as well as the lymph nodes metastases (LNM) themselves in 88 BC patients. We showed that luminal N– PT have the lowest activation of the EMT process (27%), in comparison to N+ PT (48%, p=0.06). On the other hand, TNBC do not show statistically significant EMT activation at the stage before lymph colonization (N–, 83%) and after colonization of the lymph nodes (N+, 63%, p=0.58). TNBC are also the least plastic (unable to change the EMT phenotype) in terms of turning EMT on or off between matched PT and LNM (0% EMT plasticity in TNBC vs 36% plasticity in luminal tumours). Moreover, in TNBC activation of EMT was correlated with increased cell division rate of the PT– in mesenchymal TNBC PT median Ki-67 was 45% in comparison to 10% in epithelial TNBC PT (p=0.002), whereas in PT of luminal subtypes Ki-67 did not differ between epithelial and mesenchymal phenotypes. Profiling of immunotranscriptome of epithelial and mesenchymal luminal BC with Nanostring technology revealed that N– PT with epithelial phenotype were enriched in inflammatory response signatures, whereas N+ mesenchymal cancers showed elevated MHC class II antigen presentation. Overall, activation of EMT changes during cancer progression and metastatic colonization of the lymph nodes depending on the PT molecular subtype and is related to differences in stromal signatures. Activation of EMT is associated with colonizing phenotype in luminal PT and proliferative phenotype of TNBC.

Cancer Stem Cell Regulated Phenotypic Plasticity Protects Metastasized Cancer Cells from Ferroptosis

Cancer cells display phenotypic equilibrium between the stem-like and differentiated states during neoplastic homeostasis. The functional and mechanistic implications of this subpopulation plasticity remain largely unknown. Herein, it was demonstrated that the breast cancer stem cell (BCSC) secretome autonomously compressed the stem cell population. Co-implantation with BCSCs decreased the tumor-initiating capacity yet increased metastasis of accompanying cancer cells, wherein DKK1 was identified as a pivotal factor secreted by BCSCs for such functions. DKK1-promoted differentiation was indispensable for disseminated tumor cell metastatic outgrowth. In contrast, DKK1 inhibitors substantially relieved the metastatic burden by restraining metastatic cells in the dormant state. DKK1 increased the expression of SLC7A11 to protect metastasizing cancer cells from lipid peroxidation and ferroptosis. Combined treatment with ferroptosis inducer and DKK1 inhibitor exhibited synergistic effects in diminishing metastasis. Hence, this study deciphers the contribution of CSC-regulated phenotypic plasticity in metastatic colonization and provides therapeutic approaches to limit metastatic outgrowth.