Determination of genes and microRNAs involved in the resistance to fludarabine in vivo in chronic lymphocytic leukemia

Specific Roles of MicroRNAs in Their Interactions with Environmental Factors

MicroRNAs (miRNAs) have emerged as critical regulators of gene expression by modulating numerous target mRNAs expression at posttranscriptional level. Extensive studies have shown that miRNAs are critical in various important biological processes, including cell growth, proliferation, differentiation, development, and apoptosis. In terms of their importance, miRNA dysfunction has been associated with a broad range of diseases. Increased number of studies have shown that miRNAs can functionally interact with a wide spectrum of environmental factors (EFs) including drugs, industrial materials, virus and bacterial pathogens, cigarette smoking, alcohol, nutrition, sleep, exercise, stress, and radiation. More importantly, the interactions between miRNAs and EFs have been shown to play critical roles in determining abnormal phenotypes and diseases. In this paper, we propose an outline of the current knowledge about specific roles of miRNAs in their interactions with various EFs and analyze the literatures detailing miRNAs-EFs interactions in the context of various of diseases.

Aberrant microRNA expression and its implications in the pathogenesis of leukemias

BACKGROUND

MicroRNAs (miRNAs) are a class of non-coding, endogenous, small RNAs that negatively regulate gene expression by inducing degradation or translational inhibition of target mRNAs. Aberrant expression of miRNAs appears to be a common characteristic of hematological malignancies including leukemias.

AIM

Here we review the available data supporting a role of aberrant expression of miRNAs in the pathogenesis of leukemias including acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML), and chronic lymphocytic leukemia (CLL).

CONCLUSIONS

The expression signatures of miRNAs provide exciting opportunities in the diagnosis, prognosis, and therapy of leukemia. Since miRNAs can function as either oncogenes or tumor suppressor genes in leukemogenesis, the potential of using these small RNAs as therapeutic targets opens up new opportunities for leukemia therapy by either inhibiting or augmenting their activity.

A bioinformatics filtering strategy for identifying radiation response biomarker candidates

The number of biomarker candidates is often much larger than the number of clinical patient data points available, which motivates the use of a rational candidate variable filtering methodology. The goal of this paper is to apply such a bioinformatics filtering process to isolate a modest number (<10) of key interacting genes and their associated single nucleotide polymorphisms involved in radiation response, and to ultimately serve as a basis for using clinical datasets to identify new biomarkers. In step 1, we surveyed the literature on genetic and protein correlates to radiation response, in vivo or in vitro, across cellular, animal, and human studies. In step 2, we analyzed two publicly available microarray datasets and identified genes in which mRNA expression changed in response to radiation. Combining results from Step 1 and Step 2, we identified 20 genes that were common to all three sources. As a final step, a curated database of protein interactions was used to generate the most statistically reliable protein interaction network among any subset of the 20 genes resulting from Steps 1 and 2, resulting in identification of a small, tightly interacting network with 7 out of 20 input genes. We further ranked the genes in terms of likely importance, based on their location within the network using a graph-based scoring function. The resulting core interacting network provides an attractive set of genes likely to be important to radiation response.

Epigenomics of leukemia: from mechanisms to therapeutic applications

Leukemogenesis is a multistep process in which successive transformational events enhance the ability of a clonal population arising from hematopoietic progenitor cells to proliferate, differentiate and survive. Clinically and pathologically, leukemia is subdivided into four main categories: chronic lymphocytic leukemia, chronic myeloid leukemia, acute lymphocytic leukemia and acute myeloid leukemia. Leukemia has been previously considered only as a genetic disease. However, in recent years, significant advances have been made in the elucidation of the leukemogenesis-associated processes. Thus, we have come to understand that epigenetic alterations including DNA methylation, histone modifications and miRNA are involved in the permanent changes of gene expression controlling the leukemia phenotype. In this article, we will focus on the epigenetic defects associated with leukemia and their implications as biomarkers for diagnostic, prognostic and therapeutic applications.

SULFs in human neoplasia: implication as progression and prognosis factors

Background

The sulfation pattern of heparan sulfate chains influences signaling events mediated by heparan sulfate proteoglycans located on cell surface. SULF1 and SULF2 are two endosulfatases able to cleave specific 6-O sulfate groups within the heparan chains. Their action can modulate signaling processes, many of which with key relevance for cancer development and expansion. SULF1 has been associated with tumor suppressor effects in various models of cancer, whereas SULF2 dysregulation was in relation with protumorigenic actions. However, other observations argue for contradictory effects of these sulfatases in cancer, suggesting the complexity of their action in the tumor microenvironment.

Methods

We compared the expression of the genes encoding SULF1, SULF2 and heparan sulfate proteoglycans in a large panel of cancer samples to their normal tissue counterparts using publicly available gene expression data, including the data obtained from two cohorts of newly-diagnosed multiple myeloma patients, the Oncomine Cancer Microarray database, the Amazonia data base and the ITTACA database. We also analysed prognosis data in relation with these databases.

Results

We demonstrated that SULF2 expression in primary multiple myeloma cells was associated with a poor prognosis in two independent large cohorts of patients. It remained an independent predictor when considered together with conventional multiple myeloma prognosis factors. Besides, we observed an over-representation of SULF2 gene expression in skin cancer, colorectal carcinoma, testicular teratoma and liver cancer compared to their normal tissue counterpart. We found that SULF2 was significantly over-expressed in high grade uveal melanoma compared to low grade and in patients presenting colorectal carcinoma compared to benign colon adenoma.

We observed that, in addition to previous observations, SULF1 gene expression was increased in T prolymphocytic leukemia, acute myeloid leukemia and in renal carcinoma compared to corresponding normal tissues. Furthermore, we found that high SULF1 expression was associated with a poor prognosis in lung adenocarcinoma.

Finally, SULF1 and SULF2 were simultaneously overexpressed in 6 cancer types: brain, breast, head and neck, renal, skin and testicular cancers.

Conclusions

SULF1 and SULF2 are overexpressed in various human cancer types and can be associated to progression and prognosis. Targeting SULF1 and/or SULF2 could be interesting strategies to develop novel cancer therapies.

MicroRNAs as therapeutic targets in cancer

Cancer remains a worldwide epidemic. An improved understanding of the underlying molecular mechanisms and development of effective targeted therapies are still required for many deadly cancers. The discovery of microRNAs (miRNAs or miRs) nearly 20 years ago introduced a new layer of complexity to gene regulation, but it also afforded us the opportunity to further our understanding of the molecular pathogenesis of cancers. Dysregulation of miRNAs is fundamental to the pathogenesis of many cancers based on their involvement in basic cellular functions. In addition, these previously underrecognized, noncoding RNAs have the capacity to target tens to hundreds of genes simultaneously. Thus, they are attractive candidates as prognostic biomarkers and therapeutic targets in cancer. However, several challenges remain in translating our current understanding of miRNAs to clinical therapies. Herein, we provide a review of the current knowledge of miRNAs in both solid and hematological malignancies with a focus on their potential application as therapeutic targets in cancer.

Circulating microRNAs: potential biomarkers for cancer

Cancer is the leading cause of death in the world. Development of minimally invasive biomarkers for early detection of cancer is urgently needed to reduce high morbidity and mortality associated with malignancy. MicroRNAs (miRNAs) are small regulatory RNAs that modulate the activity of specific mRNA targets and play important roles in a wide range of physiologic and pathologic processes. Recently, miRNAs were found to be dysregulated in a variety of diseases including cancer. Emerging evidence suggests that miRNAs are involved in tumor initiation and progression. Together, the different expression profiles of miRNAs in cancer, and the stability of circulating miRNAs, make them new potentially clinical biomarkers for cancer diagnosis, classification, therapeutic decisions, and prognosis.

MicroRNA in chronic lymphocytic leukemia: transitioning from laboratory-based investigation to clinical application

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia among adults in the Western world, with an incidence of approximately 1 out of 100,000 patients per year. CLL is characterized by the clonal expansion of immature CD5(+) B cells. Although cytotoxic agents remain the mainstay of therapy, the disease of up to 20% of patients is not controlled with standard therapies. Therefore, there remains a need for novel therapeutic strategies. MicroRNAs (miRNAs or miRs), first identified nearly two decades ago, are noncoding RNAs that have the capacity for simultaneous regulation of tens to hundreds of genes. An association between CLL-associated chromosomal abnormalities and miRNA deregulation is beginning to emerge. miRNAs may play a biological role in the pathogenesis of CLL: specific miRNAs (miR-15a and miR-16-1) are located at a chromosomal region (13q14.3) that is often absent in patients with CLL. These same miRNAs are relevant to cellular phenotype and in vivo development of disease. This finding has led to a rapidly expanding series of investigations linking miRNAs to CLL. As a result, miRNAs are currently under investigation as diagnostic and prognostic biomarkers as well as potential therapeutic targets in CLL.

Sulfatase 2 protects hepatocellular carcinoma cells against apoptosis induced by the PI3K inhibitor LY294002 and ERK and JNK kinase inhibitors

BACKGROUND

Sulfatase 2 (SULF2), an extracellular heparan sulphate 6-O-endosulphatase, has an oncogenic effect in hepatocellular carcinoma (HCC) that is partially mediated through glypican 3, which promotes heparin-binding growth factor signalling and HCC cell growth. SULF2 also increases phosphorylation of the anti-apoptotic Akt kinase substrate GSK3β and SULF2 expression is associated with a decreased apoptotic index in human HCCs.

METHODS

We investigated the functional and mechanistic effects of SULF2 on drug-induced apoptosis of HCC cells using immunohistochemistry, Western immunoblotting, gene transfection, real-time quantitative polymerase chain reaction, MTT and apoptosis assays and immunocytochemistry.

RESULTS

The increased expression of SULF2 in human HCCs was confirmed by immunohistochemistry and immunoblotting. Treatment with inhibitors of MEK, JNK and PI3 kinases decreased the viability of SULF2-negative Hep3B HCC cells and induced apoptotic caspase 3 and 7 activity, which was most strongly induced by the PI3K inhibitor LY294002. Forced expression of SULF2 in Hep3B cells significantly decreased activity of the apoptotic caspases 3 and 7 and induced resistance to LY294002-induced apoptosis. As expected, LY294002 inhibited activation of Akt kinase by PI3K. Conversely, knockdown of SULF2 using an shRNA construct targeting the SULF2 mRNA induced profound cell growth arrest and sensitized the endogenously SULF2-expressing HCC cell lines Huh7 and SNU182 to drug-induced apoptosis. The effects of knockdown of SULF2 on HCC cells were mediated by decreased Akt phosphorylation, downregulation of cyclin D1 and the anti-apoptotic molecule Bcl-2, and upregulation of the pro-apoptotic molecule BAD.

CONCLUSION

The prosurvival, anti-apoptotic effect of SULF2 in HCC is mediated through activation of the PI3K/Akt pathway.