Palbociclib as an early-line treatment for Japanese patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: a review of clinical trial and real-world data.

Breast cancer is the most common type of cancer among women worldwide and in Japan. The majority of breast cancers are hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2‒), and endocrine therapy is an effective therapy for this type of breast cancer. However, recent substantial advances have been made in the management of HR+/HER2‒ advanced breast cancer (ABC) with the advent of targeted therapies, such as cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, resulting in significant improvements in survival outcomes versus endocrine therapy alone. To evaluate the optimal use of palbociclib, a CDK4/6 inhibitor, in HR+/HER2- ABC, this review summarizes clinical trial and real-world data for palbociclib. In addition, current biomarker studies in palbociclib clinical research are reviewed. In Japanese patients, palbociclib was shown to be effective with a manageable safety profile, although differences were observed in the frequency of adverse event and dosing parameters. Current evidence supporting palbociclib as a first-line treatment strategy for patients with HR+/HER2‒ ABC in Asia, and specifically japan, is also discussed.

Cancer-secreted hsa-miR-940 induces an osteoblastic phenotype in the bone metastatic microenvironment via targeting ARHGAP1 and FAM134A.

Bone metastatic lesions are classified as osteoblastic or osteolytic lesions. Prostate and breast cancer patients frequently exhibit osteoblastic-type and osteolytic-type bone metastasis, respectively. In metastatic lesions, tumor cells interact with many different cell types, including osteoblasts, osteoclasts, and mesenchymal stem cells, resulting in an osteoblastic or osteolytic phenotype. However, the mechanisms responsible for the modification of bone remodeling have not been fully elucidated. MicroRNAs (miRNAs) are transferred between cells via exosomes and serve as intercellular communication tools, and numerous studies have demonstrated that cancer-secreted miRNAs are capable of modifying the tumor microenvironment. Thus, cancer-secreted miRNAs can induce an osteoblastic or osteolytic phenotype in the bone metastatic microenvironment. In this study, we performed a comprehensive expression analysis of exosomal miRNAs secreted by several human cancer cell lines and identified eight types of human miRNAs that were highly expressed in exosomes from osteoblastic phenotype-inducing prostate cancer cell lines. One of these miRNAs, hsa-miR-940, significantly promoted the osteogenic differentiation of human mesenchymal stem cells in vitro by targeting ARHGAP1 and FAM134A Interestingly, although MDA-MB-231 breast cancer cells are commonly known as an osteolytic phenotype-inducing cancer cell line, the implantation of miR-940-overexpressing MDA-MB-231 cells induced extensive osteoblastic lesions in the resulting tumors by facilitating the osteogenic differentiation of host mesenchymal cells. Our results suggest that the phenotypes of bone metastases can be induced by miRNAs secreted by cancer cells in the bone microenvironment.

Extracellular vesicles as biomarkers and therapeutic targets for cancer.

Extracellular vesicles (EVs) are small lipid membrane vesicles that are secreted from almost all kinds of cells into the extracellular space. EVs are widely accepted to be involved in various cellular processes; in particular, EVs derived from cancer cells have been reported to play important roles in modifying the tumor microenvironment and promoting tumor progression. In addition, EVs derived from cancer cells encapsulate various kinds of tumor-specific molecules, such as proteins and RNAs, which contribute to cancer malignancy. Therefore, the unveiling of the precise mechanism of intercellular communication via EVs in cancer patients will provide a novel strategy for cancer treatment. Furthermore, a focus on the contents of EVs could promote the use of EVs in body fluids as clinically useful diagnostic and prognostic biomarkers. In this review, we summarize the current research knowledge on EVs as biomarkers and therapeutic targets and discuss their potential clinical applications.

The miR-1908/SRM regulatory axis contributes to extracellular vesicle secretion in prostate cancer.

Targeting extracellular vesicle (EV) secretion can have potential clinical implications for cancer therapy, however the precise regulatory mechanisms of EV secretion are not fully understood. Recently, we have shown a novel pathway of EV biogenesis in PCa cell lines, PC3 and PC3M. However, as the characteristics of EVs are divergent even among PCa cell lines, we hypothesized that other pathways or common regulatory pathways of EV biogenesis still exist. Here, we performed quantitative high-throughput screening to determine the key regulatory genes involved in EV biogenesis in 22Rv1 cells, which secrete a different type of EVs. In total, 1728 miRNAs were screened and miR-1908 was selected as the potential miRNA regulating EV biogenesis in 22Rv1 cells. Subsequently, we investigated target genes of miR-1908 using siRNA screening and identified that spermidine synthase (SRM) was the key regulator of EV secretion in 22Rv1 cells. Attenuation of SRM expression significantly inhibited secretion of EVs in 22Rv1 cells, and overexpression of SRM was confirmed in PCa tissues. Furthermore, we found that the number of endosome compartments was increased in cellular cytoplasm after knockdown of the SRM gene. In conclusion, our results showed that miR-1908-mediated regulation of SRM can control secretion of EVs in PCa. In addition, these data suggested that the EV secretion pathway was dependent on cellular characteristics.

Epithelial-mesenchymal transition transcription factors control pluripotent adult stem cell migration in vivo in planarians.

Migration of stem cells underpins the physiology of metazoan animals. For tissues to be maintained, stem cells and their progeny must migrate and differentiate in the correct positions. This need is even more acute after tissue damage by wounding or pathogenic infection. Inappropriate migration also underpins metastasis. Despite this, few mechanistic studies address stem cell migration during repair or homeostasis in adult tissues. Here, we present a shielded X-ray irradiation assay that allows us to follow stem cell migration in planarians. We demonstrate the use of this system to study the molecular control of stem cell migration and show that snail-1, snail-2 and zeb-1 EMT transcription factor homologs are necessary for cell migration to wound sites and for the establishment of migratory cell morphology. We also observed that stem cells undergo homeostatic migration to anterior regions that lack local stem cells, in the absence of injury, maintaining tissue homeostasis. This requires the polarity determinant notum Our work establishes planarians as a suitable model for further in-depth study of the processes controlling stem cell migration in vivo.

The abrogation of condensin function provides independent evidence for defining the self-renewing population of pluripotent stem cells.

Heterogeneity of planarian stem cells has been categorised on the basis of single cell expression analyses and subsequent experiments to demonstrate lineage relationships. Some data suggest that despite heterogeneity in gene expression amongst cells in the cell cycle, in fact only one sub-population, known as sigma neoblasts, can self-renew. Without the tools to perform live in vivo lineage analysis, we instead took an alternative approach to provide independent evidence for defining the self-renewing stem cell population. We exploited the role of highly conserved condensin family genes to functionally assay neoblast self-renewal properties. Condensins are involved in forming properly condensed chromosomes to allow cell division to proceed during mitosis, and their abrogation inhibits mitosis and can lead to repeated endoreplication of the genome in cells that make repeated attempts to divide. We find that planarians possess only the condensin I complex, and that this is required for normal stem cell function. Abrogation of condensin function led to rapid stem cell depletion accompanied by the appearance of 'giant' cells with increased DNA content. Using previously discovered markers of heterogeneity we show that enlarged cells are always from the sigma-class of the neoblast population and we never observe evidence for endoreplication for the other neoblast subclasses. Overall, our data establish that condensins are essential for stem cell maintenance and provide independent evidence that only sigma-neoblasts are capable of multiple rounds of cell division and hence self-renewal.

Cross-talk between cancer cells and their neighbors via miRNA in extracellular vesicles: an emerging player in cancer metastasis.

Cancer metastasis is the major cause of mortality in cancer cases and is responsible for cancer deaths. It is known that cancer cells communicate with surrounding microenvironmental cells, such as fibroblast cells, immune cells, and endothelial cells, to create a cancer microenvironment for their progression. Extracellular vesicles (EVs) are small vesicles that can be secreted by most types of cells and play an important role in cell-to-cell communications via transferring bioactive cargos, including variable RNAs, such as microRNAs (miRNAs), to recipient cells. miRNAs are a class of small noncoding RNAs that posttranscriptionally regulate gene expression. The transfer of them to recipient cells influences the metastatic process of primary tumors. In this review, we summarize the function of miRNAs packaged in EVs in cancer metastasis and discuss the clinical utility of miRNAs in EVs.

Latest advances in extracellular vesicles: from bench to bedside.

Extracellular vesicles (EVs) are small membraned vesicles and approximately 50-150 nm in diameter. Almost all of the type of cells releases the EVs and circulates in the body fluids. EVs contain multiple functional components, such as mRNAs, microRNAs (miRNAs), DNAs, and proteins, which can be transferred to the recipient cells, resulting in phenotypic changes. Recently, EV research has focused on their potential as a drug delivery vehicle and in targeted therapy against specific molecules. Moreover, some surface proteins are specific to particular diseases, and therefore, EVs also have promise as biomarkers. In this concise review, we summarize the latest research focused on EVs, which have the potential to become a promising drug delivery method, biomarker, and new therapeutic target for improving the outcomes of cancer patients.

Extracellular vesicles: Toward a clinical application in urological cancer treatment.

Extracellular vesicles are nanometer-sized lipid membranous vesicles that are released from almost all types of cells into the extracellular space. Extracellular vesicles have gained considerable attention in the past decade, and emerging evidence suggests that they play novel roles in mediating cancer biology. Extracellular vesicles contain pathogenic components, such as proteins, DNA fragments, messenger ribonucleic acids, non-coding ribonucleic acids and lipids, all of which mediate paracrine signaling in the tumor microenvironment. Extracellular vesicles impact the multistep process of cancer progression through modulation of the immune system, angiogenesis and pre-metastatic niche formation through transfer of their contents. Therefore, a better understanding of their roles in urological cancers will provide opportunities for novel therapeutic strategies. In addition, the contents of extracellular vesicles hold promise for the discovery of liquid-based biomarkers for prostate, kidney and bladder cancers. Here, we summarize the current research regarding extracellular vesicles in urological cancer and discuss potential clinical applications for extracellular vesicles in urological cancer.

The clinical relevance of the miR-197/CKS1B/STAT3-mediated PD-L1 network in chemoresistant non-small-cell lung cancer.

Programmed cell death ligand-1 (PD-L1) has recently gained considerable attention for its role in tumor immune escape. Here, we identify a miR-197/CKS1B/STAT3-mediated PD-L1 network in chemoresistant non-small-cell lung cancer (NSCLC), independent of immunoinhibitory signals. miR-197 is downregulated in platinum-resistant NSCLC specimens, resulting in the promotion of chemoresistance, tumorigenicity, and pulmonary metastasis in vitro and in vivo. Mechanistic investigations reveal that a miR-197-mediated CKS1B/STAT3 axis exerts tumor progression regulated by various oncogenic genes (Bcl-2, c-Myc, and cyclin D1), and PD-L1 is a putative biomarker of this axis. Furthermore, we demonstrate that a miR-197 mimic sensitizes PD-L1(high) drug-resistant cells to chemotherapy. These results indicate that the biological interaction between PD-L1 and chemoresistance occurs through the microRNA regulatory cascade. More importantly, expression levels of miR-197 are inversely correlated with PD-L1 expression (n = 177; P = 0.026) and are associated with worse overall survival (P = 0.015). Our discoveries suggest that the miR-197/CKS1B/STAT3-mediated network can drive tumor PD-L1 expression as a biomarker of this cascade, and miR-197 replacement therapy may be a potential treatment strategy for chemoresistant NSCLC.

Clinical relevance and therapeutic significance of microRNA-133a expression profiles and functions in malignant osteosarcoma-initiating cells.

Novel strategies against treatment-resistant tumor cells remain a challenging but promising therapeutic approach. Despite accumulated evidence suggesting the presence of highly malignant cell populations within tumors, the unsolved issues such as in vivo targeting and clinical relevance remain. Here, we report a preclinical trial based on the identified molecular mechanisms underlying osteosarcoma-initiating cells and their clinical relevance. We identified key microRNAs (miRNAs) that were deregulated in a highly malignant CD133(high) population and found that miR-133a regulated the cell invasion that characterizes a lethal tumor phenotype. Silencing of miR-133a with locked nucleic acid (LNA) reduced cell invasion of this cell population, and systemic administration of LNA along with chemotherapy suppressed lung metastasis and prolonged the survival of osteosarcoma-bearing mice. Furthermore, in a clinical study, high expression levels of CD133 and miR-133a were significantly correlated with poor prognosis, whereas high expression levels of the four miR-133a target genes were correlated with good prognosis. Overall, silencing of miR-133a with concurrent chemotherapy would represent a novel strategy that targets multiple regulatory pathways associated with metastasis of the malignant cell population within osteosarcoma.

Bovine milk exosomes contain microRNA and mRNA and are taken up by human macrophages.

We reported previously that microRNA (miRNA) are present in whey fractions of human breast milk, bovine milk, and rat milk. Moreover, we also confirmed that so many mRNA species are present in rat milk whey. These RNA were resistant to acidic conditions and to RNase, but were degraded by detergent. Thus, these RNA are likely packaged in membrane vesicles such as exosomes. However, functional extracellular circulating RNA in bodily fluids, such as blood miRNA, are present in various forms. In the current study, we used bovine raw milk and total RNA purified from exosomes (prepared by ultracentrifugation) and ultracentrifuged supernatants, and analyzed them using miRNA and mRNA microarrays to clarify which miRNA and mRNA species are present in exosomes, and which species exist in other forms. Microarray analyses revealed that most mRNA in milk whey were present in exosomes, whereas miRNA in milk whey were present in supernatant as well as exosomes. The RNA in exosomes might exert functional effects because of their stability. Therefore, we also investigated whether bovine milk-derived exosomes could affect human cells using THP-1 cells. Flow cytometry and fluorescent microscopy studies revealed that bovine milk exosomes were incorporated into differentiated THP-1 cells. These results suggest that bovine milk exosomes might have effects in human cells by containing RNA.

The roles of extracellular vesicles in cancer biology: toward the development of novel cancer biomarkers.

Recent important progress in cancer biology was the identification of the significant roles played by extracellular vesicles (EVs). EVs are secreted by a variety of mammalian cell types and have been revealed to play important roles in intercellular communications. EVs serve as unique communication vehicles in many ways. First, unlike cytokine signaling, EVs enable transportation not only of proteins, but also of nucleic acids, including mRNAs and microRNAs. Recent reports showing the functionality of these nucleic acids in the recipient cells have opened up a new avenue of cell-to-cell communication research. Second, EVs have been revealed to transport membrane components including receptors, such as epithelial growth factor receptor. These findings have provided significant insights into understanding the molecular mechanisms of cancer development. Third, EVs protect their contents from clearance by degrading enzymes present in the extracellular space, which allows for remote transportation of the contents, even between organs. This concept is highlighted by recent reports that suggest the deep involvement of cancer cell derived EVs in metastasis. From these points of view, we will summarize recent studies on the relevance of EVs in cancer biology. We will also highlight the possibility of novel diagnostic technologies using circulating EVs in body fluid.

Neutral sphingomyelinase 2 (nSMase2)-dependent exosomal transfer of angiogenic microRNAs regulate cancer cell metastasis.

The release of humoral factors between cancer cells and the microenvironmental cells is critical for metastasis; however, the roles of secreted miRNAs in non-cell autonomous cancer progression against microenvironmental cells remain largely unknown. Here, we demonstrate that the neutral sphyngomyelinase 2 (nSMase2) regulates exosomal microRNA (miRNA) secretion and promotes angiogenesis within the tumor microenvironment as well as metastasis. We demonstrate a requirement for nSMase2-mediated cancer cell exosomal miRNAs in the regulation of metastasis through the induction of angiogenesis in inoculated tumors. In addition, miR-210, released by metastatic cancer cells, was shown to transport to endothelial cells and suppress the expression of specific target genes, which resulted in enhanced angiogenesis. These findings suggest that the horizontal transfer of exosomal miRNAs from cancer cells can dictate the microenviromental niche for the benefit of the cancer cell, like "on demand system" for cancer cells.

RPN2-mediated glycosylation of tetraspanin CD63 regulates breast cancer cell malignancy.

BACKGROUND: The tetraspanin CD63 is a highly N-glycosylated protein that is known to regulate cancer malignancy. However, the contribution of glycosylation of CD63 to cancer malignancy remains unclear. Previously, we reported that ribophorin II (RPN2), which is part of an N-oligosaccharyle transferase complex, is responsible for drug resistance in breast cancer cells. In this study, we demonstrate that cancer malignancy associated with the glycosylation of CD63 is regulated by RPN2. RESULTS: Inhibition of RPN2 expression led to a reduction in CD63 glycosylation. In addition, the localization of CD63 was deregulated by knockdown of RPN2. Interestingly, multidrug resistance protein 1 (MDR1) localization was displaced from the cell surface in CD63-silenced cells. CD63 silencing reduced the chemoresistance and invasion ability of malignant breast cancer cells. Furthermore, the enrichment of CD63/MDR1-double positive cells was associated with lymph node metastasis. Taken together, these results indicated that high glycosylation of CD63 by RPN2 is implicated in clinical outcomes in breast cancer patients. CONCLUSIONS: These findings describe a novel and important function of RPN2-mediated CD63 glycosylation, which regulates MDR1 localization and cancer malignancy, including drug resistance and invasion.

Physiological and pathological relevance of secretory microRNAs and a perspective on their clinical application.

MicroRNAs (miRNAs) have attracted significant attention because of their important roles in a variety of physiological and pathological processes. Recent studies have shown that many cell types secrete miRNAs by packaging them into lipid-bilayered small vesicles called exosomes. Furthermore, exosomal miRNAs travel between cells, exert their RNAi effects in the recipient cells, and play important roles in various biological processes. In this article, we will summarize and describe the latest studies on exosomal miRNAs by focusing on their roles in cancer progression, immune regulation, and tissue repair. We will also provide a perspective on the clinical applications of this research field.

miR-148a plays a pivotal role in the liver by promoting the hepatospecific phenotype and suppressing the invasiveness of transformed cells.

UNLABELLED: MicroRNAs (miRNAs) are evolutionary conserved small RNAs that post-transcriptionally regulate the expression of target genes. To date, the role of miRNAs in liver development is not fully understood. By using an experimental model that allows the induced and controlled differentiation of mouse fetal hepatoblasts (MFHs) into mature hepatocytes, we identified miR-148a as a hepatospecific miRNA highly expressed in adult liver. The main finding of this study revealed that miR-148a was critical for hepatic differentiation through the direct targeting of DNA methyltransferase (DNMT) 1, a major enzyme responsible for epigenetic silencing, thereby allowing the promotion of the "adult liver" phenotype. It was also confirmed that the reduction of DNMT1 by RNA interference significantly promoted the expression of the major hepatic biomarkers. In addition to the essential role of miR-148a in hepatocyte maturation, we identified its beneficial effect through the repression of hepatocellular carcinoma (HCC) cell malignancy. miR-148a expression was frequently down-regulated in biopsies of HCC patients as well as in mouse and human HCC cell lines. Overexpressing miR-148a led to an enhancement of albumin production and a drastic inhibition of the invasive properties of HCC cells, whereas miR-148a silencing had the opposite consequences. Finally, we showed that miR-148a exerted its tumor-suppressive effect by regulating the c-Met oncogene, regardless of the DNMT1 expression level. CONCLUSION: miR-148a is essential for the physiology of the liver because it promotes the hepatospecific phenotype and acts as a tumor suppressor. Most important, this report is the first to demonstrate a functional role for a specific miRNA in liver development through regulation of the DNMT1 enzyme.

Dark side of the exosome: the role of the exosome in cancer metastasis and targeting the exosome as a strategy for cancer therapy.

Cell-cell communication is essential for the regulation of various biological phenomena in multicellular organisms, including development and homeostasis. Deregulation of these interactions leads to inappropriate cell-cell communication, resulting in disease development. Cancer cells communicate closely with the cells in their microenvironment, and this communication promotes malignancy via abnormal growth, invasion, drug resistance and metastasis. Understanding cell-cell interactions in cancer is essential for the development of novel anticancer agents. As a result, discovering the communication tools used by cancer cells is important to understanding these interactions. In this review, we summarize the recent findings regarding exosome-mediated cancer development. In addition, we propose that targeting the exosome represents a novel strategy for cancer therapy.

Therapeutic effects of microRNA-582-5p and -3p on the inhibition of bladder cancer progression.

Many reports have indicated that the abnormal expression of microRNAs (miRNAs) is associated with the progression of disease and have identified miRNAs as attractive targets for therapeutic intervention. However, the bifunctional mechanisms of miRNA guide and passenger strands in RNA interference (RNAi) therapy have not yet been clarified. Here, we show that miRNA (miR)-582-5p and -3p, which are strongly decreased in high-grade bladder cancer clinical samples, regulate tumor progression in vitro and in vivo. Significantly, the overexpression of miR-582-5p or -3p reduced the proliferation and invasion of UM-UC-3 human bladder cancer cells. Furthermore, transurethral injections of synthetic miR-582 molecule suppressed tumor growth and metastasis in an animal model of bladder cancer. Most interestingly, our study revealed that both strands of miR-582-5p and -3p suppressed the expression of the same set of target genes such as protein geranylgeranyltransferase type I beta subunit (PGGT1B), leucine-rich repeat kinase 2 (LRRK2) and DIX domain containing 1 (DIXDC1). Knockdown of these genes using small interfering RNA (siRNA) resulted in the inhibition of cell growth and invasiveness of UM-UC-3. These findings uncover the unique regulatory pathway involving tumor suppression by both strands of a single miRNA that is a potential therapeutic target in the treatment of invasive bladder cancer.

Real-world progression-free survival and overall survival of palbociclib plus endocrine therapy (ET) in Japanese patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer in the first-line or second-line setting: an observational study.

BACKGROUND: A recent large real-world study conducted in the United States reported the effectiveness of palbociclib plus aromatase inhibitor in HR+/HER2- advanced breast cancer (ABC). However, local clinical practice and available medical treatment can vary between Japan and Western countries. Thus, it is important to investigate Japanese real-world data. This observational, multicenter study (NCT05399329) reports the interim analysis of effectiveness of palbociclib plus ET as first-line or second-line treatment for HR+/HER2- ABC by estimating real-world progression-free survival (rwPFS) and overall survival (OS) in Japanese routine clinical practice. METHODS: Real-world clinical outcomes and treatment patterns of palbociclib plus ET were captured using a medical record review of patients diagnosed with HR+/HER2- ABC who had received palbociclib plus ET in the first-line or second-line treatment across 20 sites in Japan. The primary endpoint was rwPFS; secondary endpoints were OS, real-world overall response rate, real-world clinical benefit rate, and chemotherapy-free survival. RESULTS: Of the 677 eligible patients, 420 and 257 patients, respectively, had received palbociclib with ET as first-line and second-line treatments. Median rwPFS (95% confidence interval) was 24.5 months (19.9-29.4) for first-line and 14.5 months (10.2-19.0) for second-line treatment groups. Median OS was not reached in the first-line group and was 46.7 months (38.8-not estimated) for the second-line group. The 36-month OS rates for de novo metastasis, treatment-free interval (TFI) ≥ 12 months, and TFI < 12 months were 80.2% (69.1-87.7), 82.0% (70.7-89.3), and 66.0% (57.9-72.9), respectively. CONCLUSION: The addition of palbociclib to ET was effective for treating HR+/HER2- ABC in Japanese routine clinical practice.