Copy number variants (CNVs) are associated with changes in gene expression levels and contribute to various adaptive traits. Here we show that a CNV at the Grain Length on Chromosome 7 (GL7) locus contributes to grain size diversity in rice (Oryza sativa L.). GL7 encodes a protein homologous to Arabidopsis thaliana LONGIFOLIA proteins, which regulate longitudinal cell elongation. Tandem duplication of a 17.1-kb segment at the GL7 locus leads to upregulation of GL7 and downregulation of its nearby negative regulator, resulting in an increase in grain length and improvement of grain appearance quality. Sequence analysis indicates that allelic variants of GL7 and its negative regulator are associated with grain size diversity and that the CNV at the GL7 locus was selected for and used in breeding. Our work suggests that pyramiding beneficial alleles of GL7 and other yield- and quality-related genes may improve the breeding of elite rice varieties.

MicroRNAs play important roles in regulating tumour development, progression and metastasis. Here we show that one of the miR-200 family members, miR-141, is under-expressed in several prostate cancer (PCa) stem/progenitor cell populations in both xenograft and primary patient tumours. Enforced expression of miR-141 in CD44+ and bulk PCa cells inhibits cancer stem cell properties including holoclone and sphere formation, as well as invasion, and suppresses tumour regeneration and metastasis. Moreover, miR-141 expression enforces a strong epithelial phenotype with a partial loss of mesenchymal phenotype. Whole-genome RNA sequencing uncovers novel miR-141-regulated molecular targets in PCa cells including the Rho GTPase family members (for example, CDC42, CDC42EP3, RAC1 and ARPC5) and stem cell molecules CD44 and EZH2, all of which are validated as direct and functionally relevant targets of miR-141. Our results suggest that miR-141 employs multiple mechanisms to obstruct tumour growth and metastasis.

MicroRNA-128 (miR-128) is reduced in prostate cancer (PCa) relative to normal/benign prostate tissues but causal roles are obscure. Here we show that exogenously introduced miR-128 suppresses tumor regeneration in multiple PCa xenograft models. Cancer stem-like cell (CSC) associated properties were blocked, including holoclone and sphere formation as well as clonogenic survival. Using a miR-128 sensor to distinguish cells on the basis of miR-128 expression, we found that miR-128-lo cells possessed higher clonal, clonogenic and tumorigenic activities than miR-128-hi cells. miR-128 targets the stem cell regulatory factors BMI-1, NANOG, and TGFBR1, the expression of which we found to vary inversely with miR-128 expression in PCa stem/progenitor cell populations. In particular, we defined BMI-1 as a direct and functionally relevant target of miR-128 in PCa cells, where these genes were reciprocally expressed and exhibited opposing biological functions. Our results define a tumor suppressor function for miR-128 in PCa by limiting CSC properties mediated by BMI-1 and other central stem cell regulators, with potential implications for PCa gene therapy.

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Purpose We have shown that the phenotypically undifferentiated (PSA−/lo) prostate cancer (PCa) cell population harbors long-term self-renewing cancer stem cells (CSCs) that resist castration and a subset of the cells within PSA−/lo population bearing the ALDHhiCD44+α2β1+ phenotype (Triple Marker+/TM+) is capable of robustly initiating xenograft tumors in castrated mice. The goal of the current project is to further characterize the biological properties of TM+ PCa cell population, particularly in the context of initiating and propagating CRPC. Experimental Design The in vivo CSC activities were measured by limiting-dilution serial tumor transplantation assays in both androgen-dependent (AD) and androgen-independent (AI) PCa xenograft models. In vitro clonal, clonogenic and sphere-formation assays were conducted in cells purified from xenograft and patient tumors. qPCR, Western blot, lentiviral-mediated gene knockdown, and human microRNA arrays were performed for mechanistic studies. Results By focusing on LAPC9 model, we show that the TM+ cells are CSCs with both tumor-initiating and tumor-propagating abilities for CRPC. Moreover, primary patient samples have TM+ cells, which possess CSC activities in ‘castrated’ culture conditions. Mechanistically, we find that 1) the phenotypic markers are causally involved in CRPC development; 2) the TM+ cells preferentially express castration resistance and stem cell-associated molecules that regulate their CSC characteristics; and 3) the TM+ cells possess distinct microRNA expression profiles and miR-499-5p functions as an oncomir. Conclusions Our results define the TM+ PCa cells as a population of pre-existent stem-like cancer cells that can both mediate and propagate CRPC and highlight the TM+ cell population as a therapeutic target.

BackgroundUnder saline conditions, plant growth is depressed via osmotic stress and salt can accumulate in leaves leading to further depression of growth due to reduced photosynthesis and gas exchange. Aquaporins are proposed to have a major role in growth of plants via their impact on root water uptake and leaf gas exchange. In this study, soybean plasma membrane intrinsic protein 1;6 (GmPIP1;6) was constitutively overexpressed to evaluate the function of GmPIP1;6 in growth regulation and salt tolerance in soybean.ResultsGmPIP1;6 is highly expressed in roots as well as reproductive tissues and the protein targeted to the plasma membrane in onion epidermis. Treatment with 100 mM NaCl resulted in reduced expression initially, then after 3 days the expression was increased in root and leaves. The effects of constitutive overexpression of GmPIP1;6 in soybean was examined under normal and salt stress conditions. Overexpression in 2 independent lines resulted in enhanced leaf gas exchange, but not growth under normal conditions compared to wild type (WT). With 100 mM NaCl, net assimilation was much higher in the GmPIP1;6-Oe and growth was enhanced relative to WT. GmPIP1;6-Oe plants did not have higher root hydraulic conductance (Lo) under normal conditions, but were able to maintain Lo under saline conditions compared to WT which decreased Lo. GmPIP1;6-Oe lines grown in the field had increased yield resulting mainly from increased seed size.ConclusionsThe general impact of overexpression of GmPIP1;6 suggests that it may be a multifunctional aquaporin involved in root water transport, photosynthesis and seed loading. GmPIP1;6 is a valuable gene for genetic engineering to improve soybean yield and salt tolerance.

Summary Melanoma cells actively participate in tumor angiogenesis and vasculogenic mimicry. However, anti‐angiogenic therapy in patients with melanoma has not shown a significant survival gain. Thus, new anti‐melanoma angiogenic and vasculogenic drugs are highly desired. Using the metastatic melanoma cell line C8161 as a model, we explored melanoma vasculogenic inhibitors and found that lycorine hydrochloride (LH) effectively suppressed C8161 cell‐dominant formation of capillary‐like tubes in vitro and generation of tumor blood vessels in vivo with low toxicity. Mechanistic studies revealed that LH markedly hindered expression of VE‐cadherin in C8161 cells, but did not affect expression of six other important angiogenic and vasculogenic genes. Luciferase assays showed that LH significantly impeded promoter activity of the VE‐cadherin gene in a dose‐dependent manner. Together, these data suggest that LH inhibits melanoma C8161 cell‐dominant vasculogenic mimicry by reducing VE‐cadherin gene expression and diminishing cell surface exposure of the protein.

Overwhelming evidence indicates that virtually all treatment-naive tumors contain a subpopulation of cancer cells that possess some stem cell traits and properties and are operationally defined as cancer cell stem cells (CSCs). CSCs manifest inherent heterogeneity in that they may exist in an epithelial and proliferative state or a mesenchymal non-proliferative and invasive state. Spontaneous tumor progression, therapeutic treatments, and (epi)genetic mutations may also induce plasticity in non-CSCs and reprogram them into stem-like cancer cells. Intrinsic cancer cell heterogeneity and induced cancer cell plasticity, constantly and dynamically, generate a pool of CSC subpopulations with varying levels of epigenomic stability and stemness. Despite the dynamic and transient nature of CSCs, they play fundamental roles in mediating therapy resistance and tumor relapse. It is now clear that the stemness of CSCs is coordinately regulated by genetic factors and epigenetic mechanisms. Here, in this perspective, we first provide a brief updated overview of CSCs. We then focus on microRNA-34a (miR-34a), a tumor-suppressive microRNA (miRNA) devoid in many CSCs and advanced tumors. Being a member of the miR-34 family, miR-34a was identified as a p53 target in 2007. It is a bona fide tumor suppressor, and its expression is dysregulated and downregulated in various human cancers. By targeting stemness factors such as NOTCH, MYC, BCL-2, and CD44, miR-34a epigenetically and negatively regulates the functional properties of CSCs. We shall briefly discuss potential reasons behind the failure of the first-in-class clinical trial of MRX34, a liposomal miR-34a mimic. Finally, we offer several clinical settings where miR-34a can potentially be deployed to therapeutically target CSCs and advanced, therapy-resistant, and p53-mutant tumors in order to overcome therapy resistance and curb tumor relapse.