MicroRNAs as Post-Transcriptional Machines and their Interplay with Cellular Networks

Identification and functional screening of microRNAs highly deregulated in colorectal cancer

MicroRNAs (miRNAs) constitute a robust regulatory network with post-transcriptional regulatory efficiency for almost one half of human coding genes, including oncogenes and tumour suppressors. We determined the expression profile of 667 miRNAs in colorectal cancer (CRC) tissues and paired non-tumoural tissues and identified 42 differentially expressed miRNAs. We chose miR-215, miR-375, miR-378, miR-422a and miR-135b for further validation on an independent cohort of 125 clinically characterized CRC patients and for in vitro analyses. MiR-215, miR-375, miR-378 and miR-422a were significantly decreased, whereas miR-135b was increased in CRC tumour tissues. Levels of miR-215 and miR-422a correlated with clinical stage. MiR-135b was associated with higher pre-operative serum levels of CEA and CA19-9. In vitro analyses showed that ectopic expression of miR-215 decreases viability and migration, increases apoptosis and promotes cell cycle arrest in DLD-1 and HCT-116 colon cancer cell lines. Similarly, overexpression of miR-375 and inhibition of miR-135b led to decreased viability. Finally, restoration of miR-378, miR-422a and miR-375 inhibited G1/S transition. These findings indicate that miR-378, miR-375, miR-422a and miR-215 play an important role in CRC as tumour suppressors, whereas miR-135b functions as an oncogene; both groups of miRNA contribute to CRC pathogenesis.

Identification and functional screening of microRNAs highly deregulated in colorectal cancer

MicroRNAs (miRNAs) constitute a robust regulatory network with post-transcriptional regulatory efficiency for almost one half of human coding genes, including oncogenes and tumour suppressors. We determined the expression profile of 667 miRNAs in colorectal cancer (CRC) tissues and paired non-tumoural tissues and identified 42 differentially expressed miRNAs. We chose miR-215, miR-375, miR-378, miR-422a and miR-135b for further validation on an independent cohort of 125 clinically characterized CRC patients and for in vitro analyses. MiR-215, miR-375, miR-378 and miR-422a were significantly decreased, whereas miR-135b was increased in CRC tumour tissues. Levels of miR-215 and miR-422a correlated with clinical stage. MiR-135b was associated with higher pre-operative serum levels of CEA and CA19-9. In vitro analyses showed that ectopic expression of miR-215 decreases viability and migration, increases apoptosis and promotes cell cycle arrest in DLD-1 and HCT-116 colon cancer cell lines. Similarly, overexpression of miR-375 and inhibition of miR-135b led to decreased viability. Finally, restoration of miR-378, miR-422a and miR-375 inhibited G1/S transition. These findings indicate that miR-378, miR-375, miR-422a and miR-215 play an important role in CRC as tumour suppressors, whereas miR-135b functions as an oncogene; both groups of miRNA contribute to CRC pathogenesis.

MicroRNAs and HIV-1 infection: antiviral activities and beyond

Cellular microRNAs (miRNAs) are an important class of small, non-coding RNAs that bind to host mRNAs based on sequence complementarity and regulate protein expression. They play important roles in controlling key cellular processes including cellular inception, differentiation and death. While several viruses have been shown to encode for viral miRNAs, controversy persists over the expression of a functional miRNA encoded in the human immunodeficiency virus type 1 (HIV-1) genome. However, it has been reported that HIV-1 infectivity is influenced by cellular miRNAs. Either through directly targeting the viral genome or by targeting host cellular proteins required for successful virus replication, multiple cellular miRNAs seem to modulate HIV-1 infection and replication. Perhaps as a survival strategy, HIV-1 may modulate proteins in the miRNA biogenesis pathway to subvert miRNA-induced antiviral effects. Global expression profiles of cellular miRNAs have also identified alterations of specific miRNAs post-HIV-1 infection both in vitro and in vivo (in various infected patient cohorts), suggesting potential roles for miRNAs in pathogenesis and disease progression. However, little attention has been devoted in understanding the roles played by these miRNAs at a cellular level. In this manuscript, we review past and current findings pertaining to the field of miRNA and HIV-1 interplay. In addition, we suggest strategies to exploit miRNAs therapeutically for curbing HIV-1 infectivity, replication and latency since they hold an untapped potential that deserves further investigation.

Extracellular vesicles modulate the glioblastoma microenvironment via a tumor suppression signaling network directed by miR-1

Extracellular vesicles have emerged as important mediators of intercellular communication in cancer, including by conveying tumor-promoting microRNAs between cells, but their regulation is poorly understood. In this study, we report the findings of a comparative microRNA profiling and functional analysis in human glioblastoma that identifies miR-1 as an orchestrator of extracellular vesicle function and glioblastoma growth and invasion. Ectopic expression of miR-1 in glioblastoma cells blocked in vivo growth, neovascularization, and invasiveness. These effects were associated with a role for miR-1 in intercellular communication in the microenvironment mediated by extracellular vesicles released by cancer stem-like glioblastoma cells. An extracellular vesicle-dependent phenotype defined by glioblastoma invasion, neurosphere growth, and endothelial tube formation was mitigated by loading miR-1 into glioblastoma-derived extracellular vesicles. Protein cargo in extracellular vesicles was characterized to learn how miR-1 directed extracellular vesicle function. The mRNA encoding Annexin A2 (ANXA2), one of the most abundant proteins in glioblastoma-derived extracellular vesicles, was found to be a direct target of miR-1 control. In addition, extracellular vesicle-derived miR-1 along with other ANXA2 extracellular vesicle networking partners targeted multiple pro-oncogenic signals in cells within the glioblastoma microenvironment. Together, our results showed how extracellular vesicle signaling promotes the malignant character of glioblastoma and how ectopic expression of miR-1 can mitigate this character, with possible implications for how to develop a unique miRNA-based therapy for glioblastoma management.

Involvement of eukaryotic small RNA pathways in host defense and viral pathogenesis

Post-transcriptional gene regulation by small RNAs is now established as an important branch of the gene regulatory system. Many different classes of small RNAs have been discovered; among these are short interfering RNAs (siRNAs) and microRNA (miRNAs). Though differences in the processing and function of small RNAs exist between plants and animals, both groups utilize small RNA-mediated gene regulation in response to pathogens. Host encoded miRNAs and siRNAs are generated from viral RNA function in host defense and pathogenic resistance in plants. In animals, miRNAs are key regulators in both immune system development and in immune function. Pathogens, in particular viruses, have evolved mechanisms to usurp the host’s small RNA-mediated regulatory system. Overall, small RNAs are a major component of host defense and immunity in eukaryotes. The goal of this review is to summarize our current knowledge of the involvement of eukaryotic small RNA pathways in host defense and viral pathogenesis.

Strong reduction of AGO2 expression in melanoma and cellular consequences

Background:

Processing of microRNAs (miRNAs) is a highly controlled process. Deregulation of miRNA expression was observed in several types of cancer but changes in the miRNA-processing enzymes have not been analysed until today. In this study, we analysed Argonaute2 (AGO2, EIF2C2), as one main factor of the miRNA processing ensemble, in the context of cancer development, especially in melanoma.

Methods:

We determined the AGO2 expression level in melanoma, as well as in other cancers, with biochemical approaches (qRT–PCR, western blot and immunofluorescence studies) and analysed the cell behaviour in migration assays.

Results:

Specifically in melanoma, we revealed a strong reduction of AGO2 expression compared with primary melanocytes. The reduction of AGO2 expression was only found on protein level, whereas the mRNA level stayed unchanged hinting to post-transcriptional regulation. We could show that re-expression of AGO2 in melanoma leads to a strong improvement of regulatory effects due to increased functionality of small-interfering RNAs and short hairpin RNAs.

Conclusion:

We identified melanoma-specific downregulation of AGO2 and corresponding reduced RNAi efficiency. These findings will help to understand the molecular basis of malignant melanoma and can potentially lead to an improvement of therapeutic strategies.

MicroRNA hsa-miR-125a-3p activates p53 and induces apoptosis in lung cancer cells

The mature microRNA hsa-miR-125a-3p is derived from the 3' end of pre-miR-125a. Here, we reported that hsa-miR-125a-3p suppressed proliferation and induced apoptosis in A549 cells. In addition, wild-type p53 mRNA and protein expression was increased by hsa-miR-125a-3p over-expression. Moreover, blocking wild-type p53 attenuated the effect of hsa-miR-125a-3p on apoptosis but could not restore completely. In p53-deficient cell line H1299, hsa-miR-125a-3p still induced apoptosis. Taken together, these data suggest that hsa-miR-125a-3p induces apoptosis not only via the p53 pathway in human lung cancer cells. These results provide new insight into the roles of the miR-125a family in lung cancer.

Potential role of human-specific genes, human-specific microRNAs and human-specific non-coding regulatory RNAs in the pathogenesis of systemic sclerosis and Sjögren's syndrome

The etiology and pathogenesis of human autoimmune diseases remain unknown despite intensive investigations. Although remarkable progress has been accomplished through genome wide association studies in the identification of genetic factors that may predispose to their occurrence or modify their clinical presentation to date no specific gene abnormalities have been conclusively demonstrated to be responsible for these diseases. The completion of the human and chimpanzee genome sequencing has opened up novel opportunities to examine the possible contribution of human specific genes and other regulatory elements unique to the human genome, such as microRNAs and non-coding RNAs, towards the pathogenesis of a variety of human disorders. Thus, it is likely that these human specific genes and non-coding regulatory elements may be involved in the development or the pathogenesis of various disorders that do not occur in non-human primates including certain autoimmune diseases such as Systemic Sclerosis and Primary Sjögren's Syndrome. Here, we discuss recent evidence supporting the notion that human specific genes or human specific microRNA and other non-coding RNA regulatory elements unique to the human genome may participate in the development or in the pathogenesis of Systemic Sclerosis and Primary Sjögren's Syndrome.

Spatiotemporal control of microRNA function using light-activated antagomirs

MicroRNAs (miRNAs) are small non-coding RNAs that act as post-transcriptional gene regulators and have been shown to regulate many biological processes including embryonal development, cell differentiation, apoptosis, and proliferation. Variations in the expression of certain miRNAs have been linked to a wide range of human diseases - especially cancer - and the diversity of miRNA targets suggests that they are involved in various cellular networks. Several tools have been developed to control the function of individual miRNAs and have been applied to study their biogenesis, biological role, and therapeutic potential; however, common methods lack a precise level of control that allows for the study of miRNA function with high spatial and temporal resolution. Light-activated miRNA antagomirs for mature miR-122 and miR-21 were developed through the site-specific installation of caging groups on the bases of selected nucleotides. Installation of caged nucleotides led to complete inhibition of the antagomir-miRNA hybridization and thus inactivation of antagomir function. The miRNA-inhibitory activity of the caged antagomirs was fully restored upon decaging through a brief UV irradiation. The synthesized antagomirs were applied to the photochemical regulation of miRNA function in mammalian cells. Moreover, spatial control over antagomir activity was obtained in mammalian cells through localized UV exposure. The presented approach enables the precise regulation of miRNA function and miRNA networks with unprecedented spatial and temporal resolution using UV irradiation and can be extended to any miRNA of interest.

Systematic transcriptome wide analysis of lncRNA-miRNA interactions

BACKGROUND

Long noncoding RNAs (lncRNAs) are a recently discovered class of non-protein coding RNAs, which have now increasingly been shown to be involved in a wide variety of biological processes as regulatory molecules. The functional role of many of the members of this class has been an enigma, except a few of them like Malat and HOTAIR. Little is known regarding the regulatory interactions between noncoding RNA classes. Recent reports have suggested that lncRNAs could potentially interact with other classes of non-coding RNAs including microRNAs (miRNAs) and modulate their regulatory role through interactions. We hypothesized that lncRNAs could participate as a layer of regulatory interactions with miRNAs. The availability of genome-scale datasets for Argonaute targets across human transcriptome has prompted us to reconstruct a genome-scale network of interactions between miRNAs and lncRNAs.

RESULTS

We used well characterized experimental Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation (PAR-CLIP) datasets and the recent genome-wide annotations for lncRNAs in public domain to construct a comprehensive transcriptome-wide map of miRNA regulatory elements. Comparative analysis revealed that in addition to targeting protein-coding transcripts, miRNAs could also potentially target lncRNAs, thus participating in a novel layer of regulatory interactions between noncoding RNA classes. Furthermore, we have modeled one example of miRNA-lncRNA interaction using a zebrafish model. We have also found that the miRNA regulatory elements have a positional preference, clustering towards the mid regions and 3' ends of the long noncoding transcripts. We also further reconstruct a genome-wide map of miRNA interactions with lncRNAs as well as messenger RNAs.

CONCLUSIONS

This analysis suggests widespread regulatory interactions between noncoding RNAs classes and suggests a novel functional role for lncRNAs. We also present the first transcriptome scale study on miRNA-lncRNA interactions and the first report of a genome-scale reconstruction of a noncoding RNA regulatory interactome involving lncRNAs.

miR-296-3p, miR-298-5p and their downstream networks are causally involved in the higher resistance of mammalian pancreatic α cells to cytokine-induced apoptosis as compared to β cells

Background

The molecular bases of mammalian pancreatic α cells higher resistance than β to proinflammatory cytokines are very poorly defined. MicroRNAs are master regulators of cell networks, but only scanty data are available on their transcriptome in these cells and its alterations in diabetes mellitus.

Results

Through high-throughput real-time PCR, we analyzed the steady state microRNA transcriptome of murine pancreatic α (αTC1-6) and β (βTC1) cells: their comparison demonstrated significant differences. We also characterized the alterations of αTC1-6 cells microRNA transcriptome after treatment with proinflammatory cytokines. We focused our study on two microRNAs, miR-296-3p and miR-298-5p, which were: (1) specifically expressed at steady state in αTC1-6, but not in βTC1 or INS-1 cells; (2) significantly downregulated in αTC1-6 cells after treatment with cytokines in comparison to untreated controls. These microRNAs share more targets than expected by chance and were co-expressed in αTC1-6 during a 6–48 h time course treatment with cytokines. The genes encoding them are physically clustered in the murine and human genome. By exploiting specific microRNA mimics, we demonstrated that experimental upregulation of miR-296-3p and miR-298-5p raised the propensity to apoptosis of transfected and cytokine-treated αTC1-6 cells with respect to αTC1-6 cells, treated with cytokines after transfection with scramble molecules. Both microRNAs control the expression of IGF1Rβ, its downstream targets phospho-IRS-1 and phospho-ERK, and TNFα. Our computational analysis suggests that MAFB (a transcription factor exclusively expressed in pancreatic α cells within adult rodent islets of Langerhans) controls the expression of miR-296-3p and miR-298-5p.

Conclusions

Altogether, high-throughput microRNA profiling, functional analysis with synthetic mimics and molecular characterization of modulated pathways strongly suggest that specific downregulation of miR-296-3p and miR-298-5p, coupled to upregulation of their targets as IGF1Rβ and TNFα, is a major determinant of mammalian pancreatic α cells resistance to apoptosis induction by cytokines.

MicroRNAs as potential clinical biomarkers: emerging approaches for their detection

MicroRNAs (miRNAs) have emerged as novel post-transcriptional regulators of gene expression. These short non-coding RNAs are involved in diverse biological processes and their dysregulation is often observed under diseased conditions. Therefore, miRNAs hold great potential as clinical biomarkers of physiological and pathological states and extensive efforts are underway to develop efficient approaches for their detection. We review recent advances and discuss the promises and pitfalls of emerging methods of miRNA profiling and detection.

Identification and profiling of arsenic stress-induced microRNAs in Brassica juncea

MicroRNAs (miRNAs) constitute a novel mechanism of gene regulation affecting plant development, growth, and stress response. To study the role of miRNAs in arsenic (As) stress, microarray profiling of miRNAs was performed in Brassica juncea using a custom Phalanx Plant OneArray containing 381 unique miRNA probes representing 618 miRNAs from 22 plant species. miRNA microarray hybridization of roots exposed to As for 1h and 4h revealed that a total of 69 miRNAs belonging to 18 plant miRNA families had significantly altered expression. The As-responsive miRNAs also exhibited a time- and organ-dependent change in their expression. Putative target prediction for the miRNAs suggested that they regulate various developmental processes (e.g. miR156, miR169, and miR172), sulphur uptake, transport, and assimilation (miR395, miR838, and miR854), and hormonal biosynthesis and/or function (e.g. miR319, miR167, miR164, and miR159). Notable changes were observed in the level of auxins [indole-3-acetic acid (IAA), indole-3- butyric acid, and naphthalene acetic acid], jasmonates [jasmonic acid (JA) and methyl jasmonate], and abscisic acid. The exogenous supply of JA and IAA improved growth of plants under As stress and altered expression of miR167, miR319, and miR854, suggesting interplay of hormones and miRNAs in the regulation of As response. In conclusion, the present work demonstrates the role of miRNAs and associated mechanisms in the plant's response towards As stress.

miR-150 regulates high glucose-induced cardiomyocyte hypertrophy by targeting the transcriptional co-activator p300

p300, a transcriptional co-activator with histone acetyl transferase (HAT) activity, plays an essential role in the pathogenesis of cardiomyocyte hypertrophy in response to multiple pro-hypertrophic stimuli including hyperglycemia. However, the precise mechanisms by which p300 expression is regulated remain unclear. The purpose of this study was to investigate the role of miR-150, a potential p300-targeting microRNA (miRNA), in the post-transcriptional control of p300 expression and cardiomyocyte hypertrophy induced by high glucose. We observed that the expression of miR-150 was significantly reduced, whereas the expression of p300 was strongly elevated, concomitant with cardiomyocyte hypertrophy, in the hearts of diabetic rats compared with normal controls. Similar alterations were observed in neonatal rat cardiomyocytes that had been exposed to high levels of glucose. miR-150 mimics inhibited p300 3'-UTR luciferase reporter activity, as well as endogenous p300 expression. In addition, miR-150 mimics prevented glucose-induced cardiomyocyte hypertrophy. Co-transfection with a p300 expression vector and miR-150 mimics reversed the protective effect of miR-150 on cardiomyocyte hypertrophy. We further showed that the high glucose-mediated activation of PKCβ(2) in turn mediated the down-regulation of miR-150 expression. These data demonstrated a novel upstream role for miR-150 in p300-mediated cardiomyocyte hypertrophy and revealed a previously uncharacterized miRNAs and HATs cross-talk mechanism for the hypertrophic phenotype induced by high glucose.

MicroRNA miR-125b controls melanoma progression by direct regulation of c-Jun protein expression

A fundamental event in the development and progression of malignant melanoma is the deregulation of cancer-relevant transcription factors. We recently showed that c-Jun is a main regulator of tumor progression in melanoma and thus the most important member of the AP-1 transcription factor family for this disease. Interestingly, we revealed that c-Jun expression was regulated on the post-transcriptional level and therefore speculated that miRNAs could be involved in c-Jun regulation. We determined seed sequences for miR-125b and miR-527 in the coding region of c-Jun mRNA that hints at the direct involvement of miRNA-dependent regulation on the protein level. We found that the expression of miR-125b was significantly reduced in malignant melanoma cell lines and tissue samples compared with melanocytes, whereas miR-527 remained unchanged. In further functional experiments, treatment of melanoma cells with pre-miR-125b resulted in strong suppression of cellular proliferation and migration, supporting the role of miR-125b in melanoma. In addition, transfection of pre-miR-125b led to strong downregulation of c-Jun protein but not mRNA expression in melanoma cells. Luciferase assays using reporter plasmids containing the miR-125b seed sequence in the luciferase coding region confirmed the direct interaction with miR-125b. Furthermore, immunoprecipitation of Ago-2 revealed that c-Jun mRNA accumulated in the RNA-induced silencing complex after pre-miR-125b transfection in melanoma cells. In summary, we identified an important role for miR-125b in malignant melanoma. Moreover, we demonstrated post-transcriptional regulation of c-Jun by this miRNA and showed that c-Jun is a main mediator of the effects of miR-125b on melanoma cells.

Regulatory mechanisms and clinical perspectives of miRNA in tumor radiosensitivity

MicroRNA (miRNA) influences carcinogenesis at multiple stages and it can effectively control tumor radiosensitivity by affecting DNA damage repair, cell cycle checkpoint, apoptosis, radio-related signal transduction pathways and tumor microenvironment. MiRNA also efficiently modulates tumor radiosensitivity at multiple levels by blocking the two essential non-homologous end-joining repair and homologous recombination repair pathways in the DNA damage response. It interferes with four radio-related pathways in ionizing radiation, including the PI3-K/Akt, NF-κB, MAPK and TGFβ signaling pathways. Moreover, the regulatory effect of miRNA in radiosensitivity can be enhanced when interacting with various key molecules, including H2AX, BRCA1, ATM, DNA-PK, RAD51, Chk1, Cdc25A, p53, PLK1, HIF-1 and VEGF, which are involved in these processes. Therefore, thoroughly understanding the mechanism of miRNA in tumor radiosensitivity could assist in finding novel targets to improve the radiotherapeutic effects and provide new clinical perspectives and insights for developing effective cancer treatments.

The effects of lidocaine and procaine on microRNA expression of adipocyte-derived adult stem cells

Background

The microRNA (miRNA) pathway has emerged as one of the biologic pathways implicated in stem cell regulation. miRNA is a noncoding, single-stranded RNA consisting of 20-25 nucleotides that inhibits the protein production at the step of translation. The molecular effects of lidocaine and procaine on adipose stem cells were investigated by examining RNA expression array.

Methods

Adipose stem cells were isolated from a prior abdominal liposuction procedure. The human adipose stem cells were cultured and then added to a mixture of 1 ml of culture medium plus 1 ml of 2% lidocaine or 2% procaine for the duration of 30 minutes. The expression levels of miRNAs were estimated by using peptide nucleic acid (PNA)-miRNA array analysis throughout the denaturation and hybridization processes after the isolation of miRNA. The miRNAs detected by microarray that either decreased by half fold or increased by 1.5 fold from the control level were interpreted as significant.

Results

According to microarray analysis there were 61 miRNAs in total, and no miRNA had decreased expression levels. The stem cells treatment with lidocaine showed 4 alteration of expression with miR-9a^* (1.53 fold), miR-29a (1.64 fold), miR-296-5p (1.64 fold) and miR-373 (1.94 fold). The stem cells treated with procaine showed 32 miRNAs that were significantly up-regulated with a range of 1.5 to 2.06 fold. They were stem cell differentiation-related miRNAs, apoptosis and cell cycle-associated miRNAs, immunity-associated miRNAs and hormonal response-related miRNAs.

Conclusions

Lidocaine and procaine affect the miRNA expression on adipose stem cells and the effect of procaine is more marked than that of lidocaine.

Pharmacogene regulatory elements: from discovery to applications

Regulatory elements play an important role in the variability of individual responses to drug treatment. This has been established through studies on three classes of elements that regulate RNA and protein abundance: promoters, enhancers and microRNAs. Each of these elements, and genetic variants within them, are being characterized at an exponential pace by next-generation sequencing (NGS) technologies. In this review, we outline examples of how each class of element affects drug response via regulation of drug targets, transporters and enzymes. We also discuss the impact of NGS technologies such as chromatin immunoprecipitation sequencing (ChIP-Seq) and RNA sequencing (RNA-Seq), and the ramifications of new techniques such as high-throughput chromosome capture (Hi-C), chromatin interaction analysis by paired-end tag sequencing (ChIA-PET) and massively parallel reporter assays (MPRA). NGS approaches are generating data faster than they can be analyzed, and new methods will be required to prioritize laboratory results before they are ready for the clinic. However, there is no doubt that these approaches will bring about a systems-level understanding of the interplay between genetic variants and drug response. An understanding of the importance of regulatory variants in pharmacogenomics will facilitate the identification of responders versus non-responders, the prevention of adverse effects and the optimization of therapies for individual patients.

HIF1α regulated expression of XPA contributes to cisplatin resistance in lung cancer

Factors regulating nucleotide excision repair probably contribute to the heterogenous response of advanced stage lung cancer patients to drugs such as cisplatin. Studies to identify the genes in the nucleotide excision repair pathway most closely associated with resistance to cisplatin have not been conclusive. We hypothesized that Xeroderma pigmentosum complementation group A (XPA), because of its dual role in sensing and recruiting other DNA repair proteins to the damaged template, would be critical in defining sensitivity to cisplatin. Studies were conducted to identify factors regulating transcription of XPA, to assess its role in modulating sensitivity to cisplatin and its expression in primary lung tumors. Hypoxia-inducible factor 1 alpha (HIF1α) subunit was found to bind with strong affinity to a hypoxia response element sequence in the promoter of XPA. Modulating expression of HIF1α by small interfering RNA or cobalt chloride markedly reduced or increased transcription of XPA in lung cancer cell lines, respectively. Protein levels of XPA were strongly correlated with sensitivity to cisplatin (r = 0.88; P < 0.001) in cell lines and sensitivity could be increased by small interfering RNA depletion of XPA. Expression of XPA determined in 54 primary lung tumors was elevated on average 5.2-fold when compared with normal bronchial epithelial cells and correlated with levels of HIF1α (r = 0.58; P < 0.01). Together, these studies identify XPA as a novel target for regulation by HIF1α whose modulation could impact lung cancer therapy.

Beyond nutrients: food-derived microRNAs provide cross-kingdom regulation

Food turns out to be not only the nutrient supplier for our body but also a carrier of regulatory information. Interestingly, a recent study made the discovery that some plant/food-derived microRNAs (miRNAs) accumulate in the serum of humans or plant-feeding animals, and regulate mammalian gene expression in a sequence-specific manner. The authors provided striking evidence that miRNAs could function as active signaling molecules to transport information across distinct species or even kingdoms. Although the mechanism of how miRNAs are shuttled between different organisms is still not well characterized, initial results point to the involvement of microvesicles and specific RNA-transporter-like proteins. These findings raise both speculation about the potential impact that plants may have on animal physiology at the molecular level, and an appealing possibility that food-derived miRNAs may offer us another means to deliver necessary nutrients or therapeutics to our bodies.