Human Lung Microbiome on the Way to Cancer.

Recent research on cancer-associated microbial communities led to the accumulation of data on the interplay between bacteria, immune and tumor cells, the pathways of bacterial induction of carcinogenesis, and its meaningfulness for medicine. Microbial communities that have any kind of impact on tumor progression and microorganisms associated with tumors have been defined as oncobiome. Over the last decades, a number of studies were dedicated to Helicobacter pylori and its role in the progression of stomach tumors, so this correlation can be regarded as proven. Involvement of bacteria in the induction of lung cancer has been largely ignored for a long time, though some correlations between this type of cancer and lung microbiome were established. Despite the fact that in the present the microbial impact on lung cancer progression has many confirmations, the underlying mechanisms are poorly understood. Microorganisms can contribute to tumor initiation and progression through production of bacteriotoxins and other proinflammatory factors. The purpose of this review is to organize the available data on lung cancer microbiome and its role in malignant tumor progression.

Tudor staphylococcal nuclease drives chemoresistance of non-small cell lung carcinoma cells by regulating S100A11.

Lung cancer is the leading cause of cancer-related deaths worldwide. Non-small cell lung cancer (NSCLC), the major lung cancer subtype, is characterized by high resistance to chemotherapy. Here we demonstrate that Tudor staphylococcal nuclease (SND1 or TSN) is overexpressed in NSCLC cell lines and tissues, and is important for maintaining NSCLC chemoresistance. Downregulation of TSN by RNAi in NSCLC cells led to strong potentiation of cell death in response to cisplatin. Silencing of TSN was accompanied by a significant decrease in S100A11 expression at both mRNA and protein level. Downregulation of S100A11 by RNAi resulted in enhanced sensitivity of NSCLC cells to cisplatin, oxaliplatin and 5-fluouracil. AACOCF(3), a phospholipase A(2) (PLA(2)) inhibitor, strongly abrogated chemosensitization upon silencing of S100A11 suggesting that PLA(2) inhibition by S100A11 governs the chemoresistance of NSCLC. Moreover, silencing of S100A11 stimulated mitochondrial superoxide production, which was decreased by AACOCF(3), as well as N-acetyl-L-cysteine, which also mimicked the effect of PLA(2) inhibitor on NSCLC chemosensitization upon S100A11 silencing. Thus, we present the novel TSN-S100A11-PLA(2) axis regulating superoxide-dependent apoptosis, triggered by platinum-based chemotherapeutic agents in NSCLC that may be targeted by innovative cancer therapies.

Simultaneous expression of flotillin-1, flotillin-2, stomatin and caveolin-1 in non-small cell lung cancer and soft tissue sarcomas.

BACKGROUND: At the present time, there is a lack of data about the involvement of flotillins and stomatin in the development of non-small cell lung cancer (NSCLC) and soft tissue sarcomas (STS). Moreover, changes in expression of members of different families of the microdomain-forming proteins (caveolins and SPFH-domain containing family) are usually investigated independently of each other. In this study we performed a combined analysis of flotillins, stomatin, and caveolin-1 expression in these pathologies and evaluated correlations between generated data and clinicopathological characteristics of the specimens. METHODS: The protein and mRNA expression was analyzed by Western blotting and real-time PCR, respectively, in tissue specimens of patients undergoing surgery for non-small cell lung cancer and soft tissue sarcomas. Association between expression of studied proteins and patient clinicopathological characteristics or outcome was evaluated. RESULTS: Stomatin protein expression was down-regulated in 80% of NSCLC samples and this decrease significantly associated with presence of lymph node metastases. Flotillin-2 protein expression was up-regulated in the majority of NSCLC samples whereas caveolin-1α expression was decreased. We revealed a strong correlation between STOM and FLOT-1 mRNA expression in both pathologies, although the gene expression changes were diverse. CONCLUSIONS: Our data demonstrate for the first time that expression of stomatin, a poorly studied microdomain-forming protein, significantly changes in human tumors, thus pointing to its importance in the progression of NSCLC. We also suggest the existence of some relationship between the expression of these proteins.

Human blood plasma proteome mapping for search of potential markers of the lung squamous cell carcinoma.

Blood plasma proteomes obtained from 77 lung squamous cell carcinoma (LSCC) patients (Stages I-III) and 67 healthy controls (all males) were analyzed by using the label-free liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the search of potential cancer biomarkers. All plasma samples were depleted of 14 highly-abundant plasma proteins by immune-affinity column chromatography before LC-MS/MS. We identified and quantified 809 differential proteins with molecular weights from 6.4 kDa to 3900 kDa using a label-free method. Three hundred and sixty four proteins were identified in all three groups. Changes in levels of an expression of blood plasma proteins associated with LSCC were discovered. Among them, 43 proteins were overexpressed and 39 proteins were down-regulated by more than two-fold between the plasmas of lung cancer patients and healthy men. We focused our attention on proteins whose expression levels increased from control to early stage and then to advanced stage tumor. Each of the 43 unique overexpressed proteins was classified according to its cellular localization, biological processes, molecular function and classes. Many of these proteins are involved in biological pathways pertinent to tumor progression and metastasis and some of these deregulated proteins may be useful clinical markers.

Comparisons of microRNA patterns in plasma before and after tumor removal reveal new biomarkers of lung squamous cell carcinoma.

Lung cancer is the major human malignancy, accounting for 30% of all cancer-related deaths worldwide. Poor survival of lung cancer patients, together with late diagnosis and resistance to classic chemotherapy, highlights the need for identification of new biomarkers for early detection. Among different cancer biomarkers, small non-coding RNAs called microRNAs (miRNAs) are considered the most promising, owing to their remarkable stability, their cancer-type specificity, and their presence in body fluids. However, results of multiple previous attempts to identify circulating miRNAs specific for lung cancer are inconsistent, likely due to two main reasons: prominent variability in blood miRNA content among individuals and difficulties in distinguishing tumor-relevant miRNAs in the blood from their non-tumor counterparts. To overcome these impediments, we compared circulating miRNA profiles in patients with lung squamous cell carcinoma (SCC) before and after tumor removal, assuming that the levels of all tumor-relevant miRNAs would drop after the surgery. Our results revealed a specific panel of the miRNAs (miR-205, -19a, -19b, -30b, and -20a) whose levels decreased strikingly in the blood of patients after lung SCC surgery. Interestingly, miRNA profiling of plasma fractions of lung SCC patients revealed high levels of these miRNA species in tumor-specific exosomes; additionally, some of these miRNAs were also found to be selectively secreted to the medium by cultivated lung cancer cells. These results strengthen the notion that tumor cells secrete miRNA-containing exosomes into circulation, and that miRNA profiling of the exosomal plasma fraction may reveal powerful cancer biomarkers.

Alterations in gene expression of proprotein convertases in human lung cancer have a limited number of scenarios.

Proprotein convertases (PCs) is a protein family which includes nine highly specific subtilisin-like serine endopeptidases in mammals. The system of PCs is involved in carcinogenesis and levels of PC mRNAs alter in cancer, which suggests expression status of PCs as a possible marker for cancer typing and prognosis. The goal of this work was to assess the information value of expression profiling of PC genes. Quantitative polymerase chain reaction was used for the first time to analyze mRNA levels of all PC genes as well as matrix metalloproteinase genes MMP2 and MMP14, which are substrates of PCs, in 30 matched pairs of samples of human lung cancer tumor and adjacent tissues without pathology. Significant changes in the expression of PCs have been revealed in tumor tissues: increased FURIN mRNA level (p<0.00005) and decreased mRNA levels of PCSK2 (p<0.007), PCSK5 (p<0.0002), PCSK7 (p<0.002), PCSK9 (p<0.00008), and MBTPS1 (p<0.00004) as well as a tendency to increase in the level of PCSK1 mRNA. Four distinct groups of samples have been identified by cluster analysis of the expression patterns of PC genes in tumor vs. normal tissue. Three of these groups covering 80% of samples feature a strong elevation in the expression of a single gene in cancer: FURIN, PCSK1, or PCSK6. Thus, the changes in the expression of PC genes have a limited number of scenarios, which may reflect different pathways of tumor development and cryptic features of tumors. This finding allows to consider the mRNAs of PC genes as potentially important tumor markers.

Suppression of basal autophagy reduces lung cancer cell proliferation and enhances caspase-dependent and -independent apoptosis by stimulating ROS formation.

Autophagy is a catabolic process involved in the turnover of organelles and macromolecules which, depending on conditions, may lead to cell death or preserve cell survival. We found that some lung cancer cell lines and tumor samples are characterized by increased levels of lipidated LC3. Inhibition of autophagy sensitized non-small cell lung carcinoma (NSCLC) cells to cisplatin-induced apoptosis; however, such response was attenuated in cells treated with etoposide. Inhibition of autophagy stimulated ROS formation and treatment with cisplatin had a synergistic effect on ROS accumulation. Using genetically encoded hydrogen peroxide probes directed to intracellular compartments we found that autophagy inhibition facilitated formation of hydrogen peroxide in the cytosol and mitochondria of cisplatin-treated cells. The enhancement of cell death under conditions of inhibited autophagy was partially dependent on caspases, however, antioxidant NAC or hydroxyl radical scavengers, but not the scavengers of superoxide or a MnSOD mimetic, reduced the release of cytochrome c and abolished the sensitization of the cells to cisplatin-induced apoptosis. Such inhibition of ROS prevented the processing and release of AIF (apoptosis-inducing factor) and HTRA2 from mitochondria. Furthermore, suppression of autophagy in NSCLC cells with active basal autophagy reduced their proliferation without significant effect on the cell-cycle distribution. Inhibition of cell proliferation delayed accumulation of cells in the S phase upon treatment with etoposide that could attenuate the execution stage of etoposide-induced apoptosis. These findings suggest that autophagy suppression leads to inhibition of NSCLC cell proliferation and sensitizes them to cisplatin-induced caspase-dependent and -independent apoptosis by stimulation of ROS formation.

Arf6 promotes cell proliferation via the PLD-mTORC1 and p38MAPK pathways.

The small G-protein ADP-ribosylation factor 6 (Arf6) belongs to the Ras GTPases superfamily and is mostly known for its actin remodeling functions and involvement in the processes of plasma membrane reorganization and vesicular transport. The majority of data indicates that Arf6 contributes to cancer progression through activation of cell motility and invasion. Alternatively, we found that the expression of a wild-type or a constitutively active Arf6 does not influence tumor cell motility and invasion but instead significantly stimulates cell proliferation and activates phospholipase D (PLD). Conversely the expression of a mutant Arf6 (Arf6N48I), that is, unable to interact with PLD has no effect on proliferation but promotes motility, invasion, and matrix degradation by uPA extracellular proteinase. Studying the mechanisms of Arf6-dependent stimulation of cell proliferation, we found some signaling pathways contributing to Arf6 promitogenic activity. Namely, we showed that Arf6 in a PLD-mTORC1-dependent manner activates S6K1 kinase, a well-known regulator of mitogen-stimulated translation initiation. Furthermore, we demonstrated an Arf6-dependent phosphorylation of mTORC1 downstream targets, 4E-BP1 and ribosomal S6 protein, confirming an existence of Arf6-PLD-mTORC1-S6K1/4E-BP1 signaling pathway and also demonstrated its impact on proliferation stimulation. Next, we found that Arf6 activation potentiates Erk1/2 and p38MAP kinases phosphorylation. Surprisingly, p38 opposite to Erk1/2 significantly contributes to Arf6-dependent proliferation increase promoting S6 ribosomal protein phosphorylation at Ser235/236 residues. Therefore, we demonstrated Arf6 proliferation stimulating activity and revealed PLD-mTORC1 and p38MAP kinase as Arf6 partners mediating promitogenic activity. These results highlight a new aspect of Arf6 functioning in cancer cell biology.

Cathepsin D messenger RNA is downregulated in human lung cancer.

OBJECTIVES: Lysosomal proteases cathepsins B and D (CB and CD) play a significant part in cancer progression. For many oncological diseases protein expression levels of CB and CD have been investigated and correlations with tumour characteristics revealed. Meanwhile, there is very little information concerning mRNA expression level. METHODS: In the present work, data about mRNA levels of CB and CD in human lung cancer was obtained using reverse transcription followed by real-time polymerase chain reaction. RESULTS: For the first time CD and CB mRNA in human lung cancer tumours was quantified. It was shown that CB and CD mRNA levels do not correlate with any tumour characteristics. However, in most analysed tumours, expression of CD mRNA was downregulated compared with adjacent normal tissue (p <0.0003). CONCLUSIONS: The data obtained indicate CD mRNA as a potential lung cancer marker.