Relation between nucleolar size and growth characteristics in small cell lung cancer cell lines

Small cell lung cancer cells express the late stage gBK tumor antigen: a possible immunotarget for the terminal disease

Big Potassium (BK) ion channels have several splice variants. One splice variant initially described within human glioma cells is called the glioma BK channel (gBK). Using a gBK-specific antibody, we detected gBK within three human small cell lung cancer (SCLC) lines. Electrophysiology revealed that functional membrane channels were found on the SCLC cells. Prolonged exposure to BK channel activators caused the SCLC cells to swell within 20 minutes and resulted in their death within five hours. Transduction of BK-negative HEK cells with gBK produced functional gBK channels. Quantitative RT-PCR analysis using primers specific for gBK, but not with a lung-specific marker, Sox11, confirmed that advanced, late-stage human SCLC tissues strongly expressed gBK mRNA. Normal human lung tissue and early, lower stage SCLC resected tissues very weakly expressed this transcript. Immunofluorescence using the anti-gBK antibody confirmed that SCLC cells taken at the time of the autopsy intensely displayed this protein. gBK may represent a late-stage marker for SCLC. HLA-A*0201 restricted human CTL were generated in vitro using gBK peptide pulsed dendritic cells. The exposure of SCLC cells to interferon-γ (IFN-γ) increased the expression of HLA; these treated cells were killed by the CTL better than non-IFN-γ treated cells even though the IFN-γ treated SCLC cells displayed diminished gBK protein expression. Prolonged incubation with recombinant IFN-γ slowed the in vitro growth and prevented transmigration of the SCLC cells, suggesting IFN-γ might inhibit tumor growth in vivo. Immunotherapy targeting gBK might impede advancement to the terminal stage of SCLC via two pathways.

Bestatin inhibits cell growth, cell division, and spore cell differentiation in Dictyostelium discoideum

Bestatin methyl ester (BME) is an inhibitor of Zn(2+)-binding aminopeptidases that inhibits cell proliferation and induces apoptosis in normal and cancer cells. We have used Dictyostelium as a model organism to study the effects of BME. Only two Zn(2+)-binding aminopeptidases have been identified in Dictyostelium to date, puromycin-sensitive aminopeptidase A and B (PsaA and PsaB). PSA from other organisms is known to regulate cell division and differentiation. Here we show that PsaA is differentially expressed throughout growth and development of Dictyostelium, and its expression is regulated by developmental morphogens. We present evidence that BME specifically interacts with PsaA and inhibits its aminopeptidase activity. Treatment of cells with BME inhibited the rate of cell growth and the frequency of cell division in growing cells and inhibited spore cell differentiation during late development. Overexpression of PsaA-GFP (where GFP is green fluorescent protein) also inhibited spore cell differentiation but did not affect growth. Using chimeras, we have identified that nuclear versus cytoplasmic localization of PsaA affects the choice between stalk or spore cell differentiation pathway. Cells that overexpressed PsaA-GFP (primarily nuclear) differentiated into stalk cells, while cells that overexpressed PsaAΔNLS2-GFP (cytoplasmic) differentiated into spores. In conclusion, we have identified that BME inhibits cell growth, division, and differentiation in Dictyostelium likely through inhibition of PsaA.

Enlarged and prominent nucleoli may be indicative of MYCN amplification: a study of neuroblastoma (Schwannian stroma-poor), undifferentiated/poorly differentiated subtype with high mitosis-karyorrhexis index

BACKGROUND

According to the International Neuroblastoma Pathology Classification, neuroblastomas exhibiting MYCN amplification (A-MYCN) have unique histologic features-namely, undifferentiated/poorly differentiated subtype with a high mitosis-karyorrhexis index (U/PD-H). Nonetheless, certain tumors possessing these histologic characteristics contain a nonamplified MYCN gene (NA-MYCN).

METHODS

The clinical characteristics of patients from the Children's Cancer Group (CCG) 3881 and 3891 studies who had neuroblastoma, U/PD-H, exhibiting A-MYCN (n=68) or NA-MYCN (n=33) were investigated. The histologic and cytologic features of tumors (A-MYCN, n=62; NA-MYCN, n=28) filed at the Pathology Reference Laboratory, Department of Pathology and Laboratory Medicine, Childrens Hospital Los Angeles, were reviewed, and nucleolar areas in undifferentiated neuroblastic cells were evaluated using image analysis methods.

RESULTS

All 68 patients whose tumors exhibited A-MYCN had disease that was in an advanced clinical stage (Stage III or IV); 89.7% of these patients were diagnosed between ages 0.5 and 3.5 years, and 67 of the 68 had been treated with the high-risk protocol in the CCG-3891 study. Children whose tumors exhibited NA-MYCN were evenly distributed across all age groups; 30 of these 33 children had advanced-stage disease, and 26 had been treated with a high-risk protocol. The prognosis associated with A-MYCN (event free survival [EFS], 15.7%; overall survival [OS], 22.2%) was significantly poorer than the prognosis associated with NA-MYCN (EFS, 56.1%; OS, 69.3%). The lone histologic/cytologic difference between tumors exhibiting A-MYCN and tumors exhibiting NA-MYCN involved nucleolar appearance. Neuroblastic cells in tumors exhibiting A-MYCN were characterized by the presence of 1 or more large, prominent nucleoli, and the mean nucleolar area was significantly greater in the 18 tumors exhibiting A-MYCN that were assessed (7.63 microm2) than in the 16 tumors exhibiting NA-MYCN that were assessed (5.53 microm2; P=0.004).

CONCLUSIONS

Neuroblastomas, U/PD-H, were found to vary in terms of molecular background and clinical behavior. The results of the current study indicate that nucleolar enlargement in neuroblastic cells may be a sign of MYCN amplification.

A novel target gene, SKP2, within the 5p13 amplicon that is frequently detected in small cell lung cancers

We investigated DNA copy-number aberrations in 22 cell lines derived from small cell lung cancers (SCLCs) using comparative genomic hybridization. A minimal common region at 5p13, within the 5p11-p13 amplicon that was most frequently involved, harbored the CDH6, PC4, and SKP2 genes. These three genes showed amplification and consequent overexpression in the SCLC cell lines. SKP2 positively regulates progression of cell cycle by targeting several regulators, such as the cell-cycle inhibitor p27(KIP1), for ubiquitin-mediated degradation. SKP2 was amplified in 7 (44%) of 16 primary SCLC tumors, and consequently overexpressed in 10 (83%) of the 12 of those tumors we examined. Expression levels of SKP2 protein were cell cycle-dependent in SCLC cells as well as in normal cells, and were correlated with the DNA copy-number of the gene. There was an inverse correlation between the expression of SKP2 and p27(KIP1) proteins. Down-regulation of SKP2 using an anti-sense oligonucleotide remarkably suppressed the growth of SCLC cells. Our results indicate that SKP2 is likely to be a target of the 5p13 amplification and to play an important role in the growth of SCLC cells.

Mass spectrometric high-throughput analysis of serum-free conditioned medium from cancer cell lines

Proteins secreted by cancer cells may be useful as tumor markers. We analyzed constituents produced by cells grown in serum-free conditioned medium to avoid confounding factors present in serum. Mass spectrometric techniques were used to obtain expression patterns of constituents between 2000 and 15000 Da from as little as 1 microl of crude sample. This protocol can produce distinctive mass profiles from 16 cell lines within 1 h. Thus, differential display by mass spectrometry will expedite the discovery of peptides specifically secreted by particular cells. These data illustrate the advantage of this strategy over the conventional approach of electrophoretic separation of serum samples.

Lack of class II transactivator causes severe deficiency of HLA-DR expression in small cell lung cancer

Small cell lung cancer (SCLC) is characteristically not associated with tumour-infiltrating lymphocytes. Since SCLC has been reported to show marked reduction of class I HLA, the reduced expression has been considered a means of escaping anti-cancer immunity. However, HLA-DR expressed in cancer cells is now known to contribute to anti-cancer immunity. To clarify the difference in HLA-DR expression between SCLC and non-small cell lung cancer (NSCLC), and the mechanism, the expression and the cis- and trans-acting factors involved were investigated. HLA-DR was not immunohistochemically detected in any SCLC and could not be induced by interferon gamma (IFN-gamma) in any SCLC cell line, whereas HLA-DR was expressed to varying degrees and was easily induced in NSCLC. SCLC cell lines lacked class II transactivator (CIITA) even after IFN-gamma induction, whereas NSCLC cell lines expressed CIITA. The other class II HLA-specific transcription factors were expressed and genomic DNA of HLA-DR, including the promoter, was conserved well both in SCLC and in NSCLC cell lines. CIITA transfection improved the expression of HLA-DR in SCLC. In conclusion, the lack of CIITA results in severe deficiency of HLA-DR expression in SCLC. Since CIITA has also been reported to induce class I HLA, CIITA transfection might make it possible to establish effective anti-cancer immunotherapy against SCLC through the up-regulation of class I and class II HLA.

Construction of expressing plasmids of recombinant FN polypeptides with bifunctional-domain and the characterization of the products expressed in E. coli

Two expressing plasmids have been constructed and used to express two bifunctional-domain recombinant polypeptides of human fibronectin (FN) in E. coli. One was CH50 (Pro1239-Ser1515 of FN linked with Ala1690-Thr1960 of FN through Met) and the other was CH56 (Pro1239-Thr1960 of FN). Both of two polypeptides were capable of binding heparin and were purified by heparin-agarose affinity chromatography. The purified products were capable of binding cells. The production of CH50 and CH56 polypeptides provided a fundamental basis for further study of the anti-metastatic function of recombinant fibronectin polypeptides.

Establishment of a human small cell lung cancer cell line producing a large amount of anti-diuretic hormone

A new cancer cell line (Lu-165) producing a large amount of anti-diuretic hormone (ADH, 2.8 micrograms/g protein) was established from a 50-year-old small cell lung cancer patient presenting with a syndrome of inappropriate anti-diuretic hormone secretion. These cells grew well in serum-supplemented medium and during more than 100 passages they continued producing a large amount of this hormone. This cell line will be a useful tool for studies of the biochemistry and pathology of ADH-producing cancer.

Levels of complement regulatory molecules in lung cancer: disappearance of the D17 epitope of CD55 in small-cell carcinoma

The levels of complement-regulatory molecules (complement receptor type one [CR1], decay-accelerating factor [DAF], membrane cofactor protein [MCP], and an inhibitor of membrane attack complex [CD59]) in lung cancer cells were analyzed to investigate the relation between their expression and histological subtypes, and the possibility of homologous complement deposition on cancer cells. In 25 cell lines (10 adenocarcinoma, 3 large-cell carcinoma, 7 small-cell lung cancer [SCLC], and 5 squamous cell carcinoma), flow cytometric analysis revealed that MCP was expressed in all cell lines, whereas none of the cell lines was CR1-positive. CD59 was detected in all cells. The DAF epitope defined by IA10 was expressed in all cells except one large cell carcinoma cell line. However, another epitope for anti-DAF monoclonal antibody, D17, was not detected in 5 (71.4%) SCLC and in 4 (22.2%) non-small-cell lung cancer. This disparity was seen in most cell lines, irrespective of histological subtypes. The loss of D17 reactivity seemed to be pertinent to malignant phenotype, because most of the normal pulmonary cells possessed the D17 epitope. Furthermore, a cell line lacking DAF (IA10-/D17-) allowed alternative pathway-mediated homologous complement (C3) deposition after pretreatment with anti-MCP antibody. This raises a new possibility for immunotargeting of cancer. These cell lines should be useful in studying the biology of lung cancer.

The impact of surgery on the multidisciplinary treatment of bronchogenic small cell carcinoma (updated review including ongoing studies)

Recent results of studies on patients with SCLC treated by surgery with curative intent followed by adjuvant chemotherapy demonstrate a definite progress in comparison to non-surgical-treatment programs for patients with comparable stage of disease. Of 186 randomized patients enrolled for the multicenter cooperative ISC-Study I and II, 76 patients with stage pT1-3N0M0 received surgery for cure followed by chemotherapy and selective radiotherapy to the brain. The projected 4 year crude survival rate by September 1991 was 57%. In 27 of 43 patients with stage pT1-3N2M0, the tumors were completely resected, resulting in a 4 year survival rate of 32%. The survival curve for both groups of patients shows a sharp bent at 27 months postoperatively, whereafter the survival curves take a plateau-like course. These promising results were confirmed by several other groups. They are in favour of initial surgery for resectable tumors, followed by postoperative chemotherapy, while patients on preoperative chemotherapy followed by adjuvant surgery showed less favourable results.