Up-regulation of RNA m6A methyltransferase like-3 expression contributes to arsenic and benzo[a]pyrene co-exposure-induced cancer stem cell-like property and tumorigenesis.

While arsenic or BaP alone exposure can cause lung cancer, studies showed that arsenic plus BaP co-exposure displays a significantly stronger lung tumorigenic effect. However, the underlying mechanism has not been well understood. Studies showed that RNA molecules are chemically modified. The most frequently occurring RNA modification in eukaryotic messenger RNAs is the N6-methyladenosine (m6A) methylation. This study aimed to determine whether arsenic plus BaP exposure alters RNA m6A methylation and its role in lung tumorigenic effect of arsenic plus BaP exposure. Human bronchial epithelial cells transformed by exposure to arsenic or BaP alone, and arsenic plus BaP and mouse xenograft tumorigenesis models were used in this study. It was found that arsenic plus BaP exposure-transformed cells have significantly higher levels of RNA m6A methylation than arsenic or BaP alone exposure-transformed human bronchial epithelial cells. Western blot analysis showed that arsenic plus BaP exposure greatly up-regulates the m6A writer methyltransferase like-3 (METTL3) expression levels in cultured cells and mouse lung tissues. METTL3 knockdown in cells transformed by arsenic plus BaP exposure drastically reduced their RNA m6A methylation levels. Functional studies revealed that METTL3 knockdown in cells transformed by arsenic plus BaP exposure greatly reduces their anchorage-dependent and -independent growth, cancer stem cell characters and tumorigenesis. The findings from this study suggest that arsenic plus BaP co-exposure causes epitranscriptomic dysregulation, which may contribute significantly to arsenic plus BaP co-exposure-caused synergistic lung tumorigenic effect.

The m6A RNA methylation regulates oncogenic signaling pathways driving cell malignant transformation and carcinogenesis.

The m6A RNA methylation is the most prevalent internal modification in mammalian mRNAs which plays critical biological roles by regulating vital cellular processes. Dysregulations of the m6A modification due to aberrant expression of its regulatory proteins are frequently observed in many pathological conditions, particularly in cancer. Normal cells undergo malignant transformation via activation or modulation of different oncogenic signaling pathways through complex mechanisms. Accumulating evidence showing regulation of oncogenic signaling pathways at the epitranscriptomic level has added an extra layer of the complexity. In particular, recent studies demonstrated that, in many types of cancers various oncogenic signaling pathways are modulated by the m6A modification in the target mRNAs as well as noncoding RNA transcripts. m6A modifications in these RNA molecules control their fate and metabolism by regulating their stability, translation or subcellular localizations. In this review we discussed recent exciting studies on oncogenic signaling pathways that are modulated by the m6A RNA modification and/or their regulators in cancer and provided perspectives for further studies. The regulation of oncogenic signaling pathways by the m6A modification and its regulators also render them as potential druggable targets for the treatment of cancer.

Low dose lead exposure at the onset of puberty disrupts spermatogenesis-related gene expression and causes abnormal spermatogenesis in mouse.

Implications of lead (Pb) exposure in dysregulated spermatogenesis in sexually active individuals during adulthood is well established; however, the effect of Pb exposure on spermatogenesis in the early stages of puberty is not clear yet. Moreover, the mechanism of Pb mediated dysregulation of spermatogenesis in adults is also poorly understood. Exposure to environmental toxicants during puberty may cause serious consequences in adulthood causing developmental retardations, especially in the reproductive system. Here we investigated the effects of lead exposure on spermatogenesis at the onset of puberty and the underlying mechanisms of these effects. Male ICR mice were exposed to low (50 mg/L) and high (200 mg/L) doses of Pb through the drinking water for 90 days. At the end of this period, the blood Pb level of the low-dose and high-dose exposure groups were found 6.14 ± 0.34 µg/dL and 11.92 ± 2.92 µg/dL respectively which were in agreement with the US CDC-recommended (5 µg/dL) and Chinese CDC-recommended (10 µg/dL) reference blood Pb level for the children. Although no visible toxicity was observed in either group, Pb exposure caused considerable histopathological changes in testis and epididymis; increased sperm DNA fragmentation indices as well as disrupted sperm heads and head-neck conjunctions. Moreover, both low and high-dose Pb exposures caused aberrant expressions of several important spermatogenesis-related genes in epididymis and testis. These results suggest that although the blood Pb levels are close to the recommended-reference values, low dose Pb exposure at the onset of puberty can disrupt spermatogenesis-related gene expression and cause abnormal mouse spermatogenesis.

Chronic Hexavalent Chromium Exposure Upregulates the RNA Methyltransferase METTL3 Expression to Promote Cell Transformation, Cancer Stem Cell-Like Property, and Tumorigenesis.

Hexavalent chromium [Cr(VI)] is a common environmental carcinogen causing lung cancer in humans. This study investigates the mechanism of Cr(VI) carcinogenesis focusing on the role of the epitranscriptomic dysregulation. The epitranscriptomic effect of Cr(VI) was determined in Cr(VI)-transformed human bronchial epithelial cells, chromate-exposed mouse and human lungs. The epitranscriptomic effect and its role in Cr(VI)-induced cell transformation, cancer stem cell (CSC)-like property, and tumorigenesis were determined by microarray analysis, soft agar colony formation, suspension spheroid formation, and mouse xenograft tumorigenesis assays. It was found that chronic Cr(VI) exposure causes epitranscriptomic dysregulations as evidenced by the increased levels of total RNA N6-methyladenosine (m6A) modification and the RNA m6A methyltransferase like-3 (METTL3) in Cr(VI)-transformed cells and chromate exposure-caused mouse and human lung tumors. Knockdown of METTL3 expression in Cr(VI)-transformed cells significantly reduces their m6A levels and transformed phenotypes and tumorigenicity in mice. Moreover, knockdown of METTL3 expression in parental nontransformed cells significantly reduces the capability of chronic Cr(VI) exposure to induce cell transformation and CSC-like property. Together, this study reveals that chronic Cr(VI) exposure is capable of altering cellular epitranscriptome by increasing the m6A RNA modification via upregulating the RNA methyltransferase METTL3 expression, which plays an important role in Cr(VI)-induced cell transformation, CSC-like property, and tumorigenesis.

Dysregulations of Functional RNA Modifications in Cancer, Cancer Stemness and Cancer Therapeutics.

More than a hundred chemical modifications in coding and non-coding RNAs have been identified so far. Many of the RNA modifications are dynamic and reversible, playing critical roles in gene regulation at the posttranscriptional level. The abundance and functions of RNA modifications are controlled mainly by the modification regulatory proteins: writers, erasers and readers. Modified RNA bases and their regulators form intricate networks which are associated with a vast array of diverse biological functions. RNA modifications are not only essential for maintaining the stability and structural integrity of the RNA molecules themselves, they are also associated with the functional outcomes and phenotypic attributes of cells. In addition to their normal biological roles, many of the RNA modifications also play important roles in various diseases particularly in cancer as evidenced that the modified RNA transcripts and their regulatory proteins are aberrantly expressed in many cancer types. This review will first summarize the most commonly reported RNA modifications and their regulations, followed by discussing recent studies on the roles of RNA modifications in cancer, cancer stemness as wells as functional RNA modification machinery as potential cancer therapeutic targets. It is concluded that, while advanced technologies have uncovered the contributions of many of RNA modifications in cancer, the underlying mechanisms are still poorly understood. Moreover, whether and how environmental pollutants, important cancer etiological factors, trigger abnormal RNA modifications and their roles in environmental carcinogenesis remain largely unknown. Further studies are needed to elucidate the mechanism of how RNA modifications promote cell malignant transformation and generation of cancer stem cells, which will lead to the development of new strategies for cancer prevention and treatment.

Role and Therapeutic Targeting of the PI3K/Akt/mTOR Signaling Pathway in Skin Cancer: A Review of Current Status and Future Trends on Natural and Synthetic Agents Therapy.

The mammalian or mechanistic target of rapamycin (mTOR) and associated phosphatidyl-inositiol 3-kinase (PI3K)/protein kinase B (Akt) pathways regulate cell growth, differentiation, migration, and survival, as well as angiogenesis and metabolism. Dysregulation of these pathways is frequently associated with genetic/epigenetic alterations and predicts poor treatment outcomes in a variety of human cancers including cutaneous malignancies like melanoma and non-melanoma skin cancers. Recently, the enhanced understanding of the molecular and genetic basis of skin dysfunction in patients with skin cancers has provided a strong basis for the development of novel therapeutic strategies for these obdurate groups of skin cancers. This review summarizes recent advances in the roles of PI3K/Akt/mTOR and their targets in the development and progression of a broad spectrum of cutaneous cancers and discusses the current progress in preclinical and clinical studies for the development of PI3K/Akt/mTOR targeted therapies with nutraceuticals and synthetic small molecule inhibitors.

Oxidizability assay of unfractionated plasma of patients' with different plasma profile: a methodological study.

BACKGROUND: Present study describe the in vitro model of plasma oxidation of patients with different lipid profile, that can be correlated to their invivo plasma oxidizability in order to find the arterial diseases prone patient groups. METHOD: The method applied here to measure the invitro plasma oxidizability, accounts a convenient way that can be well suited in any clinical laboratory settings. Un-fractionated plasma was exposed to CuSO4 (5.0 mmol/L), a pro-oxidant, and low frequency ultrasonic wave to induce oxidation, and finally oxidizability was calculated by TBARS and Conjugated Diene methods. RESULT: In our study, plasma LDL greater than 150 mg/dL possess 1.75 times more risk to undergo oxidation (CI, 0.7774 to 3.94; p = 0.071) than the low LDL plasma, percent of oxidation increased from 38.3% to 67.1% for the LDL level upto 150 mg/dL and high. Lag phase, which is considered as the plasma antioxidative protection, was also influenced by the higher LDL concentration. The mean lag time was 65.27 ± 20.02 (p = 0.02 compared to healthy), where as for 94.71 ± 35.11 min for the normolipidemic subject. The plasma oxidizability was also changed drastically for total cholesterol level, oxidative susceptibility shown 35% and 55.02% for 200 mg/dL and high respectively, however it didn't appear as risk factor. Patient samples were also stratified according to their age, gender, and blood glucose level. Older persons (≥40 years) were 1.096 times (95% CL, 0.5607 to 2.141, p = 0.396) than younger (≤39 years age), males are 1.071 (95% CI, 0.5072- 2.264) times than the females, and diabetic patients are 1.091 (CI, 0.6153 to 1.934, p = 0.391) times in more risk than the non-diabetic counterpart. CONCLUSION: This method addressing its easy applicability in biomedical research. And by this we were able to show that patients with high LDL (≥150 mg/dL) are in alarming condition besides diabetic and elderly (≥40 years age) males are considered to be susceptible and more prone to develop vascular diseases.