Antisense oligonucleotide targeting eukaryotic translation initiation factor 4E reduces growth and enhances chemosensitivity of non-small-cell lung cancer cells

Elevated levels of eukaryotic translation initiation factor 4E (eIF4E) enhance translation of many malignancy-related proteins, such as vascular endothelial growth factor (VEGF), c-Myc and osteopontin. In non-small-cell lung cancer (NSCLC), levels of eIF4E are significantly increased compared with normal lung tissue. Here, we used an antisense oligonucleotide (ASO) to inhibit the expression of eIF4E in NSCLC cell lines. eIF4E levels were significantly reduced in a dose-dependent manner in NSCLC cells treated with eIF4E-specific ASO (4EASO) compared with control ASO. Treatment of NSCLC cells with the 4EASO resulted in decreased cap-dependent complex formation, decreased cell proliferation and increased sensitivity to gemcitabine. At the molecular level, repression of eIF4E with ASO resulted in decreased expression of the oncogenic proteins VEGF, c-Myc and osteopontin, whereas expression of β-actin was unaffected. Based on these findings, we conclude that eIF4E-silencing therapy alone or in conjunction with chemotherapy represents a promising approach deserving of further investigation in future NSCLC clinical trials.

Expression of group IIa secretory phospholipase A2 increases with prostate tumor grade

PURPOSE

Arachidonate release contributes to prostate tumor progression as arachidonate is metabolized into prostaglandins and leukotrienes, potent mediators of immune suppression, cellular proliferation, tumor motility, and invasion. The group IIa sPLA2 (sPLA2-IIa) can facilitate arachidonate release from cellular phospholipids. We therefore sought to determine whether sPLA2-IIa expression might be related to the development or progression of prostatic adenocarcinoma (CaP).

EXPERIMENTAL DESIGN

sPLA2-IIa expression was examined by Western blot analyses of CaP cells and xenografts and by immunohistochemistry of benign prostatic hyperplasias and primary human CaPs (n = 101) using a sPLA2-IIa-specific polyclonal antibody.

RESULTS

sPLA2-IIa expression was increased dramatically in the androgen-independent CWR-22R and LNAI CaP cells versus the androgen-dependent CWR-22 and LNCaP cells. Immunohistochemical analyses revealed that sPLA2-IIa expression was also significantly increased with CaP development and advancing disease (trend analysis; Pearson correlation coefficient, P = 0.016). High-grade CaPs showed intense, uniform staining for sPLA2-IIa that was significantly different from that in adjacent benign prostatic hyperplasias (Fisher's exact test, P = 0.021) or low-grade CaP (P = 0.013), both of which showed only focal or weak sPLA2-IIa staining. Further, uniform sPLA2-IIa expression was directly related to the increased proliferative index that typifies advancing disease (P = 0.001). Most significantly, enhanced sPLA2-IIa expression was inversely related to 5-year patient survival (P = 0.015).

CONCLUSIONS

These data show that sPLA2-IIa expression increases with progression to androgen-independence and is highest in the most poorly-differentiated, highest-grade primary human CaP samples.

AKT-1, -2, and -3 are expressed in both normal and tumor tissues of the lung, breast, prostate, and colon

PURPOSE

The AKT/PKB kinase controls many of the intracellular processes that are dysregulated in human cancer, including the suppression of apoptosis and anoikis and the induction of cell cycle progression. Three isoforms of AKT have been identified: AKT-1, -2, and -3. Selective up-regulation of AKT-3 RNA expression has been reported in hormone-independent breast and prostate cancer cell lines suggesting that AKT-3 expression may be increased with breast or prostate tumor progression. To determine whether AKT-3 RNA expression is selectively up-regulated in human cancers and whether the patterns of AKT RNA expression may change with tumor development, we examined AKT isoform expression by RT-PCR in human cancer cell lines, primary human cancers, and normal human tissues.

EXPERIMENTAL DESIGN

AKT-1, -2, and -3 RNA expression was examined by RT-PCR. Because up-regulated AKT-3 expression has been implicated in human breast and prostate cancer progression, we also examined AKT-3 expression levels by semiquantitative RT-PCR using matched normal/tumor first-strand cDNA pairs from colon, breast, prostate, and lung cancers.

RESULTS

Our data reveal that the overwhelming majority of both normal and tumor tissues express all three of the AKT isoforms. Moreover, semiquantitative RT-PCR of matched normal/tumor pairs confirmed similar AKT-3 RNA expression levels in both normal and tumor tissue.

CONCLUSIONS

Our data show that both normal and tumor tissues express all three of the AKT isoforms and indicate that tumorigenesis does not involve a dramatic shift in the RNA expression patterns of the three AKT isoforms.

Integrin-linked kinase expression increases with prostate tumor grade

PURPOSE

Integrin-linked kinase (ILK) overexpression can suppress anoikis, promote anchorage-independent cell cycle progression, and induce tumorigenesis and invasion. Inhibition of ILK in prostatic adenocarcinoma (CaP) cells elicits cell cycle arrest and induces apoptosis. Furthermore, ILK expression increases with androgen-independent progression of human CaP cell lines, suggesting that increased ILK expression may be associated with CaP progression.

EXPERIMENTAL DESIGN

To assess whether ILK expression may be related to CaP development and/or progression, we have evaluated ILK expression by immunohistochemistry in 100 human prostate tissues.

RESULTS

We show that ILK expression increases significantly with CaP progression. ILK immunostaining is specifically increased in high-grade, primary human CaP relative to adjacent benign prostatic hyperplasia (P < 0.001), benign prostatic hyperplasia from patients without cancer (P < 0.002), and low-grade CaP (P = 0.003). ILK overexpression is specifically associated with the increased proliferative index (P = 0.001) that typifies CaP progression. Strikingly, intense uniform ILK immunostaining was inversely related to 5-year patient survival (P = 0.004).

CONCLUSIONS

ILK expression increases dramatically with CaP progression. ILK expression is also specifically related to the disproportionately increased proliferative index that contributes to the net gain of CaP cells during progression. Finally, enhanced ILK expression is inversely related to 5-year patient survival. These data therefore implicate increased ILK expression in prostate tumor progression.

Increased AKT activity contributes to prostate cancer progression by dramatically accelerating prostate tumor growth and diminishing p27Kip1 expression

The PTEN tumor suppressor gene is frequently inactivated in human prostate cancers, particularly in more advanced cancers, suggesting that the AKT/protein kinase B (PKB) kinase, which is negatively regulated by PTEN, may be involved in human prostate cancer progression. We now show that AKT activation and activity are markedly increased in androgen-independent, prostate-specific antigen-positive prostate cancer cells (LNAI cells) established from xenograft tumors of the androgen-dependent LNCaP cell line. These LNAI cells show increased expression of integrin-linked kinase, which is putatively responsible for AKT activation/Ser-473 phosphorylation, as well as for increased phosphorylation of the AKT target protein, BAD. Furthermore, expression of the p27(Kip1) cell cycle regulator was diminished in LNAI cells, consistent with the notion that AKT directly inhibits AFX/Forkhead-mediated transcription of p27(Kip1). To assess directly the impact of increased AKT activity on prostate cancer progression, an activated hAKT1 mutant was overexpressed in LNCaP cells, resulting in a 6-fold increase in xenograft tumor growth. Like LNAI cells, these transfectants showed dramatically reduced p27(Kip1) expression. Together, these data implicate increased AKT activity in prostate tumor progression and androgen independence and suggest that diminished p27(Kip1) expression, which has been repeatedly associated with prostate cancer progression, may be a consequence of increased AKT activity.

Regulation of mouse colony-stimulating factor-1 gene promoter activity by AP1 and cellular nucleic acid-binding protein

Macrophage colony-stimulating factor (M-CSF; CSF-1) is a member of a complex network of cytokines that regulate monocytic cell development and activity. It is produced in nearly all organs by cell types commonly found in connective tissue, including fibroblasts and monocytes. Whether different cell types share common or have divergent mechanisms for regulating CSF-1 gene expression is not known. To address this question, the identity of cis-acting elements and cognate trans-acting factors was characterized in a region of the CSF-1 promoter known to be more active in monocytes than in fibroblasts. The results of DNase I protection assays performed with fibroblast- or monocyte-derived nuclear extracts revealed a difference in the pattern of DNA-binding proteins. One protected region, common to both fibroblasts and monocytes, spans a putative phorbol ester-responsive element (TRE), and binding to the TRE by AP1 was verified with antibodies directed against c-fos and c-jun family members. Mutational analysis revealed that the TRE is required for CSF-1 gene expression in proliferating fibroblasts and monocytes. Binding of a second putative trans-acting factor, preferentially expressed in fibroblasts, to the region immediately upstream of the TRE was also detected. Screening a mouse expression library with oligonucleotides spanning the putative cis-acting element identified cellular nucleic acid-binding protein (CNBP) as the cognate binding activity, and antiserum to CNBP disrupted the electromobility shift assay complex. Mutational analysis revealed that loss of CNBP binding leads to a decrease in CSF-1 promoter activity in fibroblasts but has no effect on CSF-1 promoter activity in monocytes. Our results demonstrate that control of CSF-1 gene expression in monocytes and fibroblasts is mediated by common and cell type-specific trans-acting factors.

Transcriptional regulation of the mouse CSF-1 gene

Research in our laboratory is aimed at understanding the cellular and molecular mechanisms that govern colony stimulating factor-1 (CSF-1) gene expression. Our hypothesis is that a basal set of trans-acting factors is bound to the CSF-1 gene during fibroblast proliferation, resulting in constitutive CSF-1 gene expression. Modulation of CSF-1 gene transcription by growth-arrest (decrease) or stimulation of growth-arrested fibroblasts (re-initiate) is mediated by changes in the basal set of factors bound and/or by the addition of stimulus-specific factors. We have extended our hypothesis to include other cell types (monocytes) to determine if mechanisms used to control CSF-1 gene expression in fibroblasts are unique or represent common nontissue-specific regulatory mechanisms. Analysis of CSF-1-CAT reporter constructs in transiently transfected fibroblasts and monocytes was used to identify CSF-1 genomic sequences that affect transcriptional activity. DNase I protection, electrophoretic mobility shift, and methylation interference assays were used to identify the putative cis-acting elements. Results of our study suggest multiple trans-acting factors may regulate CSF-1 gene expression; some may be tissue specific, while others, such as AP1, CTF/NF1, Sp1, and Sp3, are shared in common.

Binding of a CTF/NF1-like protein to the mouse colony-stimulating factor-1 gene promoter

Circulating and tissue-specific monocytes/macrophages, through production of hydrolytic enzymes and growth factors, can dramatically affect the local tissue environment. Colony-stimulating factor-1 (CSF-1) is a key regulator of monocyte/macrophage cell activity. CSF-1 is produced by stromal elements, including fibroblasts, which are found in all tissues. To understand at the molecular level how changes in CSF-1 gene transcription are initiated in fibroblasts, we set out to identify the cis-acting elements and cognate trans-acting factor(s) that bind regulatory regions of the mouse CSF-1 gene. Analysis of heterologous reporter constructs containing the mouse CSF-1 promoter linked to the bacterial chloramphenicol acetyltransferase (CAT) gene in transiently transfected fibroblasts identified a cis-acting element located between base pairs -88 and -43 of the CSF-1 gene. Electrophoretic mobility-shift assays (EMSAs) and DNase I protection assays with nuclear extracts isolated from proliferating fibroblasts revealed distinct protein binding to the region spanning base pairs -90 to -68. Results from methylation interference assays suggest CTF/NF1 or a CTF/NF1-like factor is the cognate trans-acting factor. Mutation of the putative CTF/NF1 binding site in the CSF-1 promoter lead to a modest decrease in promoter activity in transiently transfected fibroblasts and monocytes. Therefore, we have demonstrated that CTF/NF1 or a CTF/NF1-like protein binds to the CSF-1 gene promoter; however, binding of the CTF/NF1-like protein alone does not significantly effect changes in CSF-1 gene promoter activity.