69 research outputs found
Alternative splicing in lung cancer
Abstract: Alterations in alternative splicing affect essential biologic
processes and are the basis for a number of pathologic conditions,
including cancer. In this review we will summarize the evidence
supporting the relevance of alternative splicing in lung cancer. An
example that illustrates this relevance is the altered balance between
Bcl-xL and Bcl-xS, two splice variants of the apoptosis regulator
Bcl-x. Splice modifications in cancer-related genes can be associated
with modifications either in cis-acting splicing regulatory sequences
or in trans-acting splicing factors. In fact, lung tumors show abnormal
expression of splicing regulators such as ASF/SF2 or some
members of the heterogeneous nuclear ribonucleoprotein family.
The potential significance of alternative splicing as a target for lung
cancer diagnosis or treatment will also be discussed
Complementing the cancer-immunity cycle
Reactivation of cytotoxic CD8+ T-cell responses has set a new direction for cancer
immunotherapy. Neutralizing antibodies targeting immune checkpoint programmed cell
death protein 1 (PD-1) or its ligand (PD-L1) have been particularly successful for tumor
types with limited therapeutic options such as melanoma and lung cancer. However,
reactivation of T cells is only one step toward tumor elimination, and a substantial fraction
of patients fails to respond to these therapies. In this context, combination therapies
targeting more than one of the steps of the cancer-immune cycle may provide significant
benefits. To find the best combinations, it is of upmost importance to understand the
interplay between cancer cells and all the components of the immune response. This
review focuses on the elements of the complement system that come into play in the
cancer-immunity cycle. The complement system, an essential part of innate immunity,
has emerged as a major regulator of cancer immunity. Complement effectors such
as C1q, anaphylatoxins C3a and C5a, and their receptors C3aR and C5aR1, have
been associated with tolerogenic cell death and inhibition of antitumor T-cell responses
through the recruitment and/or activation of immunosuppressive cell subpopulations
such as myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), or M2
tumor-associated macrophages (TAMs). Evidence is provided to support the idea that
complement blocks many of the effector routes associated with the cancer-immunity
cycle, providing the rationale for new therapeutic combinations aimed to enhance the
antitumor efficacy of anti-PD-1/PD-L1 checkpoint inhibitors
Novel and natural knockout lung cancer cell lines for the LKB1/STK11 tumor suppressor gene
Germline mutations of the LKB1 gene are responsible for Peutz-Jeghers syndrome (PJS), an autosomal dominant inherited disorder bestowing an increased risk of cancer. We have recently demonstrated that LKB1 inactivating mutations are not confined to PJS, but also appear in lung adenocarcinomas of sporadic origin, including primary tumors and lung cancer cell lines. To accurately determine the frequency of inactivating LKB1 gene mutations in lung tumors we have sequenced the complete coding region of LKB1 in 21 additional lung cancer cell lines. Here we describe the mutational status of LKB1 gene in 30 lung cancer cell lines from different histopathological types, including 11 lung adenocarcinomas (LADs) and 11 small cell lung cancers (SCLCs). LKB1 gene alterations were present in six (54%) of the LAD cell lines tested but in none of the other histological types. Similar to our previous observations in primary tumors, all point mutations were of the nonsense or frameshift type, leading to an abnormal, truncated protein. Moreover, 2 cell lines (A427 and H2126) harbored large gene deletions that spanned several exons. Hence, we have identified additional lung cancer cell lines carrying inactivating mutations of the LKB1 tumor suppressor gene, further attesting to the significance of this gene in the development of LADs and providing new natural LKB1 knockouts for studies of the biological function of the LKB1 protein
Adrenomedullin functions as an important tumor survival factor in human carcinogenesis
Adrenomedullin (AM) is a pluripotent regulatory peptide initially isolated from a human pheochromocytoma (adrenal tumor) and subsequently shown to play a critical role in cancer cell division, tumor neovascularization, and circumvention of programmed cell death, thus it is an important tumor cell survival factor underlying human carcinogenesis. A variety of neural and epithelial cancers have been shown to produce abundant amounts of AM. Recent findings have implicated elevation of serum AM with the onset of malignant expression. In addition, patients with tumors producing high levels of this peptide have a poor prognostic clinical outcome. Given that most human epithelial cancers display a microenvironment of reduced oxygen tension, it is interesting to note that AM and several of its receptors are upregulated during hypoxic insult. The existence of such a regulatory pathway has been implicated as the basis for the overexpression of AM/AM-R in human malignancies, thereby generating a subsequent autocrine/paracrine growth advantage for the tumor cell. Furthermore, AM has been implicated as a potential immune suppressor substance, inhibiting macrophage function and acting as a newly identified negative regulator of the complement cascade, protective properties which may help cancer cells to circumvent immune surveillance. Hence, AM's traditional participation in normal physiology (cited elsewhere in this issue) can be extended to a primary player in human carcinogenesis and may have clinical relevance as a biological target for the intervention of tumor progression
A gene-alteration profile of human lung cancer cell lines
ABSTRACT: Aberrant proteins encoded from genes altered
in tumors drive cancer development and may also be
therapeutic targets. Here we derived a comprehensive
gene-alteration profile of lung cancer cell lines. We tested
17 genes in a panel of 88 lung cancer cell lines and found
the rates of alteration to be higher than previously thought.
Nearly all cells feature inactivation at TP53 and CDKN2A
or RB1, whereas BRAF, MET, ERBB2, and NRAS
alterations were infrequent. A preferential accumulation
of alterations among histopathological types and a mutually
exclusive occurrence of alterations of CDKN2A and RB1
as well as of KRAS, epidermal growth factor receptor
(EGFR), NRAS, and ERBB2 were seen. Moreover, in nonsmall-
cell lung cancer (NSCLC), concomitant activation of
signal transduction pathways known to converge in
mammalian target of rapamycin (mTOR) was common.
Cells with single activation of ERBB2, PTEN, or MET
signaling showed greater sensitivity to cell-growth inhibition
induced by erlotinib, LY294002, and PHA665752,
respectively, than did cells featuring simultaneous activation
of these pathways, underlining the need for combined
therapeutic strategies in targeted cancer treatments. In
conclusion, our gene-alteration landscape of lung cancer
cell lines provides insights into how gene alterations
accumulate and biological pathways interact in cancer.
Hum Mutat 30, 1199–1206, 2009. & 2009Wiley-Liss, Inc
Overexpression of adrenomedullin gene markedly inhibits proliferation of PC3 prostate cancer cells in vitro and in vivo
The expression of the gene encoding adrenomedullin (AM), a multifunctional peptide hormone, in the prostate is localized to the epithelial cells. Prostate cancer cells are derived from prostatic epithelial cells. To elucidate the potential role of the AM gene in prostate cancer progression, we have stably-transfected the PC3 human prostate cancer cell line with an AM gene expression vector. The AM-transfected PC3 sublines were studied along with parental and empty vector transfected PC3 cells as controls. The average level of AM in the conditioned media of AM-transfected cells was 0.959+/-0.113 nM, a physiologically relevant concentration. The ectopic expression of AM gene inhibited the proliferation of PC3 cells in culture dishes. In addition, anchorage-independent growth of the transfected sublines was virtually abolished in soft agar assays. Flow cytometry studies showed that overexpression of AM gene caused a very significant G(1)/G(0) cell cycle arrest. In vivo experiments demonstrated that AM gene expression markedly inhibited the growth of xenograft tumors in nude mice. Our in vivo and in vitro studies suggest that AM could strongly suppress the malignancy of prostate cancer cells, via autocrine and/or paracrine mechanisms
Pharmacokinetics and antitumor efficacy of paclitaxel-cyclodextrin complexes loaded in mucus-penetrating nanoparticles for oral administration
The authors report a novel approach for enhancing the oral absorption of paclitaxel (PTX) by encapsulation in poly(anhydride) nanoparticles (NPs) containing cyclodextrins and poly(ethylene glycol). Materials & methods: Formulations were prepared using the solvent displacement method. Subsequently, pharmacokinetics and organ distribution assays were evaluated after oral administration into C57BL/6J mice. In addition, antitumor efficacy studies were performed in a subcutaneous tumor model of Lewis lung carcinoma. Results: PTX-loaded NPs displayed sizes between 190–300 nm. Oral NPs achieved drug plasma levels for at least 24 h, with an oral bioavailability of 55–80%. Organ distribution studies revealed that PTX, orally administered in NPs, underwent a similar distribution to intravenous Taxol® (Bristol-Myers-Squibb, NJ, USA). For in vivo antitumor assays, oral strategy maintained a slower tumor growth than intravenous Taxol. Conclusion: PTX orally administered in poly(anhydride) NPs, combined with cyclodextrins and poly(ethylene glycol), displayed sustained plasma levels and significant antitumor effect in a syngenic tumor model of carcinoma in mice
Expression of complement factor H by lung cancer cells: effects on the activation of the alternative pathway of complement
The complement system is important in immunosurveillance against tumors. However, malignant cells are usually resistant to complement-mediated lysis. In this study, we examine the expression of factor H, an inhibitor of complement activation, and factor H-like protein 1 (FHL-1), its alternatively spliced form, in lung cancer. We also evaluate the potential effect of factor H/FHL-1 in the protection of lung cancer cells against the activation of the complement cascade. By Northern blot analysis we demonstrate a high expression of factor H and FHL-1 in most non-small cell lung cancer cell lines, although neuroendocrine pulmonary tumors (small cell lung carcinoma and carcinoid cell lines) had undetectable levels. Western blot analysis of conditioned medium showed the active secretion of factor H and FHL-1 by cells that were positive by Northern blot. Expression of factor H/FHL-1 mRNA was also shown in a series of non-small cell lung cancer biopsies by in situ hybridization. Interestingly, many cultured lung cancer cells were able to bind fluorescence-labeled factor H to their surfaces. Deposition of C3 fragments from normal human serum on H1264, a lung adenocarcinoma cell line, was more efficient when factor H/FHL-1 activity was blocked by specific antibodies. Blocking factor H/FHL-1 activity also enhanced the release of anaphylatoxin C5a and moderately increased the susceptibility of these cells to complement-mediated cytotoxicity. In summary, we demonstrate the expression of factor H and FHL-1 by some lung cancer cells and analyze the contribution of these proteins to the protection against complement activation
Altered patterns of expression of members of the heterogeneous nuclear ribonucleoprotein (hnRNP) family in lung cancer
hnRNP A2/B1 has been suggested as a useful early detection marker for lung carcinoma. hnRNP A2/B1 is a member of a large family of heterogeneous nuclear ribonucleoproteins (hnRNP proteins) involved in a variety of functions, including regulation of transcription, mRNA metabolism, and translation. In lung cancer, we have evaluated the expression and cellular localization of several members of the hnRNP family, hnRNP A1, A2, B1, C1, C2 and K. 16 cell lines (SCLC and NSCLC) and biopsies from 32 lung cancer patients were analyzed. Our results suggest that, besides hnRNP A2/B1, the expression of other members of the hnRNP family is altered both in SCLC and NSCLC. In the biopsies, negative or low expression of the hnRNP proteins analyzed was observed in normal epithelial cells whereas lung cancer cells showed highly intense nuclear or cytoplasmic immunolocalization. In all the lung cancer cell lines, the mRNA for all the hnRNP proteins was detected. In general, higher levels of hnRNP mRNAs were found in SCLC as compared with NSCLC. Our results also suggest that the expression and processing of each hnRNP protein in lung cancer is independently regulated and is not exclusively related to proliferation status. In SCLC cell lines, hnRNP A1 protein expression correlated with that of Bcl-x(L). In the lung cancer cell lines, hnRNP K protein localization varied with the cellular confluence
Relative amounts of antagonistic splicing factors, hnRNP A1 and ASF/SF2, change during neoplastic lung growth: implications for pre-mRNA processing
Pre-mRNA processing is an important mechanism for globally modifying cellular protein composition during tumorigenesis. To understand this process during lung cancer, expression of two key pre-mRNA alternative splicing factors was compared in a mouse model of early lung carcinogenesis and during regenerative growth following reversible lung injury. Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 and alternative splicing factor/splicing factor 2 (ASF/SF2) act antagonistically to modulate splice site selection. Both hnRNP A1 and ASF/SF2 contents rose in adenomas and during injury-induced hyperplasia compared to control lungs, as measured by immunoblotting. While both proteins increased similarly during compensatory hyperplasia, hnRNP A1 increased to a much greater extent than ASF/SF2 in tumors, resulting in a 6-fold increase of the hnRNP A1 to ASF/SF2 ratio. Immunohistochemical analysis showed that hnRNP A1 localized exclusively within tumor nuclei, while ASF/SF2 appeared in cytoplasm and/or nuclei, depending on the growth pattern of the tumor cells. We also demonstrated cancer-associated changes in the pre-mRNA alternative splicing of CD44, a membrane glycoprotein involved in cell-cell and cell-extracellular matrix interactions. hnRNP A1 and ASF/SF2 expression is thus differentially altered in neoplastic lung cells by mechanisms that do not strictly arise from increased cell division. These changes are influenced by tumor histology and may be associated with production of variant CD44 mRNA isoforms
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