Induction of phenotypic changes in SCLC cell lines in vitro by hexamethylene bisacetamide, sodium butyrate, and cyclic AMP

Expression of GRP and its receptor is associated with improved survival in patients with colon cancer

Epithelial cells lining the adult human colon do not normally express gastrin releasing peptide (GRP) or its receptor (GRPR), but both can be up regulated post malignant transformation. However, controversy exists as to the contribution these proteins make to tumor cell behavior once present. Since GRPR activation promotes proliferation, it has been assumed that their aberrant expression promotes colon cancer (CC) growth and progression. Yet we have contended that when expressed, GRP/GRPR benefits the host since in vitro studies demonstrate they enhance tumor cell attachment to the extracellular matrix and promote CC cytolysis by natural killer lymphocytes. Thus the aim of this study was to ascertain the effect of aberrant GRP/GRPR expression on patient survival. To do this we identified all CC diagnosed at a single institution from 1998 to 2002 that were classified as AJCC stage II or III (n = 88); of these 50 (57%) had sufficient tissues remaining for study. GRP/GRPR expression and natural killer cell density were determined immunohistochemically at the leading edge of each CC, and survival assessed by Kaplan Meier analysis. Expression of high levels of GRPR alone, or both GRP and GRPR, was associated with delayed CC recurrence (14.1-17.0 months, respectfully; P = 0.005) and increased survival (10.1-13.1 months, respectfully; P = 0.0124). CC expressing GRP/GRPR were associated with significantly fewer lymph node metastases than tumors not expressing these proteins, and contained significantly more CD16 + natural killer cells, than tumors not expressing these proteins. These findings demonstrate that patients whose CC express GRPR are associated with a survival advantage as compared to those whose CC do not express these proteins.

Gastrin-releasing peptide mediates its morphogenic properties in human colon cancer by upregulating intracellular adhesion protein-1 (ICAM-1) via focal adhesion kinase

Gastrin-releasing peptide (GRP) and its receptor (GRPR) act as morphogens when expressed in colorectal cancer (CRC), promoting the assumption of a better differentiated phenotype by regulating cell motility in the context of remodeling and retarding tumor cell metastasis by enhancing cell-matrix attachment. Although we have shown that these processes are mediated by focal adhesion kinase (FAK), the downstream target(s) of GRP-induced FAK activation are not known. Since osteoblast differentiation is mediated by FAK-initiated upregulation of ICAM-1 (Nakayamada S, Okada Y, Saito K, Tamura M, Tanaka Y. J Biol Chem 278: 45368-45374, 2003), we determined whether GRP-induced activation of FAK alters ICAM-1 expression in CRC and, if so, determined the contribution of ICAM-1 to mediating GRP's morphogenic properties. Caco-2 and HT-29 cells variably express GRP/GRPR. These cells only express ICAM-1 when GRPR are present. In human CRC, GRPR and ICAM-1 are only expressed by better differentiated tumor cells, with ICAM-1 located at the basolateral membrane. ICAM-1 expression was only observed subsequent to GRPR signaling via FAK. To study the effect of ICAM-1 expression on tumor cell motility, CRC cells expressing GRP, GRPR, and ICAM-1 were cultured in the presence and absence of GRPR antagonist or monoclonal antibody to ICAM-1. CRC cells engaged in directed motility in the context of remodeling and were highly adherent to the extracellular matrix, only in the absence of antagonist or ICAM-1 antibody. These data indicate that GRP upregulation of ICAM-1 via FAK promotes tumor cell motility and attachment to the extracellular matrix.

Neuromedin B and its receptor are mitogens in both normal and malignant epithelial cells lining the colon

Bombesin-like peptides are uniformly thought to act as mitogens in cancer. Yet by studying human tissues, we have recently shown that bombesin and its mammalian homologue gastrin-releasing peptide act as morphogens, promoting tumor differentiation when aberrantly upregulated in colon cancer. In contrast, little is known about the bombesin-like peptide neuromedin B (NMB) and its receptor (NMB-R) in the human gastrointestinal tract. We therefore studied their presence and function in normal and malignant human colonic epithelia. Anti-NMB monoclonal antibodies were made against keyhole limpet hemocyanin (KLH)-conjugated human NMB, whereas anti-NMB-R antibodies were raised in rabbits against KLH-conjugated peptides corresponding to the third intracellular loop and COOH-terminal tail of the receptor protein. NMB antibody recognized two bands at approximately 1.2 kDa and approximately 1.5 kDa. NMB-R antibodies recognized a band at 80 kDa (predicted 43 kDa); whereas treatment with the deglycosylating agent peptide-N-glycosidase generated bands at 65, 47, and 43 kDa. By immunohistochemistry, both NMB and NMB-R were expressed in normal and cancerous colonic epithelial tissues. In cancer, the amount of NMB was similar to that expressed by proliferating epithelial cells located within the crypt. In contrast, NMB-R expression was increased in cancer, with higher levels detected in better differentiated tumor cells. To assess NMB function, proliferation was determined in the nonmalignant human colonic epithelial cell line NCM-460 and in the colon cancer cell lines Caco-2 and HT-29. Exogenously added NMB was 50-100% more efficacious than gastrin-releasing peptide in causing tumor cell proliferation, whereas only NMB increased NCM-460 cell proliferation. These findings indicate that NMB and its receptor are coexpressed by proliferating cells in which they act in an autocrine fashion with similar and modest potency in both normal and malignant colonic epithelial cells.

HMBA induces cell death and potentiates doxorubicin toxicity in malignant mesothelioma cells

PURPOSE

Malignant pleural mesothelioma(MM), a rare tumor characterized by high local invasiveness and low metastatic efficiency, is poorly responsive to current therapeutic approaches. The aim of the present study was to evaluate the cytotoxic efficacy of the hybrid polar compound hexamethylene bisacetamide(HMBA), either as a single agent or in combination with the anthracycline doxorubicin (DOX), against MM cells.

METHODS

The MM cell lines MM-B1 and MM-El were treated with HMBA, DOX or with combinations of the two drugs. Cell survival and death were assessed by the MTS assay and trypan blue staining/TUNEL, respectively. The interactions between drugs were evaluated by the method of Kern et al. Western blot analysis was used to investigate the expression of Bcl-2 family proteins.

RESULTS

When administered alone, HMBA dose-dependently decreased the number of viable cells and increased the death rate of MM-B1 and MM-E1 cultures. Combinations of HMBA and DOX achieved a synergistic inhibition of MM cell survival, and the simultaneous administration of HMBA counteracted the resistance induced by DOX in MM-El cells. HMBA,used at cytostatic concentrations, reduced the ratio be-tween antiapoptotic (Bcl-2, Bcl-XL) and proapoptotic(Bax) members of the Bcl-2 family of proteins, thus lowering the threshold for MM cell death commitment.

CONCLUSIONS

HMBA has therapeutic potential in MM both as a single agent and through potentiation of DOX toxicity. These results support future investigations on the feasibility of intrapleural chemotherapy with this hybrid polar compound.

Stimulation of the aberrant expression of a paraneoplastic antigen, recoverin, in small cell lung cancer cell lines

Recoverin, a retina-specific Ca2+-binding protein, is one of the paraneoplastic antigens (PNAs) which are normally present in neurons, but can also be aberrantly expressed in malignant tumors localized outside the nervous system. In this study, we have analyzed 16 small cell lung carcinoma (SCLC) and 12 non-small cell lung carcinoma cell lines and found that none of them is capable of expressing recoverin in vitro. However, two small cell lung carcinoma lines, NCI-H69 and NCI-H82, became recoverin-positive after cultivation in the presence of butyrate. Recoverin expression in the butyrate-treated cells has been detected by immunoblotting with polyclonal (monospecific) antibodies against recoverin and confirmed by the analysis of recoverin mRNA expression. To our knowledge, this work is the first to demonstrate stimulation of the aberrant expression of recoverin in cancer cell lines in vitro. This result opens the way to investigation of the mechanisms underlying the aberrant expression of recoverin, as well as other paraneoplastic antigens, in tumor cells.

Effects of tachyplesin on the morphology and ultrastructure of human gastric carcinoma cell line BGC-823

AIM: To investigate the morphological and ultrastructural changes in the human gastric carcinoma cell line BGC-823 after being treated with tachyplesin.

METHODS: Tachyplesin was isolated from acid extracts of Chinese horseshoe crab (Tachypleus tridentatus) hemocytes. BGC-823 cells and the cells treated with 2.0 mg/L tachyplesin were examined respectively under light microscope, scanning and transmission electron microscope.

RESULTS: BGC-823 cells had undergone the restorational alteration in morphology and ultrastructure after tachyplesin treatment. The changes were as follows: the shape of cells was unanimous, the volume enlarged and cells turned to be flat and spread, the nucleo-cytoplasmic ratio lessened and nuclear shape became rather regular, the number of nucleolus reduced and its volume lessened, heter-chromatin decreased while euchromatin increased in nucleus. In the cytoplasm, mitochondria grew in number with consistent structure relatively, Golgi complex turned to be typical and well-developed, rough endoplasmic reticulum increased and polyribosome decreased. The microvilli at cellular surface were rare and the filopodia reduced while lamellipodia increased at the cell edge.

CONCLUSION: Tachyplesin could alter the malignant morphological and ultrastructural characteristics of human gastric carcinoma cells effectively and have a certain inducing differen-tiation effect on human gastric carcinoma cells.

Reduced beta adrenoceptor density in vivo in human lung tumours: a preliminary study with positron emission tomography

BACKGROUND

Reduced beta adrenergic receptor density in tumours has been reported in previous in vitro studies. The aim of the present study was to assess whether this occurs in vivo.

METHODS

Pulmonary beta adrenoceptors were imaged and quantified in vivo using positron emission tomography (PET) and the beta antagonist radioligand (S)-[11C]CGP-12177 in five men with lung tumours of mean age 58 years (range 42-68). The histology of the tumours was squamous cell carcinoma in two cases, adenocarcinoma in one, carcinoid tumour in one, and large cell carcinoma in one. The regional blood volume and extravascular tissue density were also measured using PET. Regions of interest were drawn for both non-tumour and tumour lung tissue.

RESULTS

The mean (SD) blood volume was 0.142 (0.025) ml/ml in tumour regions and 0.108 (0.010) ml/ml in normal lung regions--a difference of 31%. Mean (SD) extravascular tissue density was 0.653 (0.133) g/ml in tumour regions, substantially higher than in normal lung regions (0.157 (0.021) g/ml). On the contrary, beta receptor density was 5.1 (1.8) pmol/g in tumour regions, lower than the value of 9.9 (1.6) pmol/g found in adjacent normal lung--a difference of 48%.

CONCLUSIONS

In vivo beta adrenoceptor density is reduced in human lung tumours.

Modulation effects of hexamethylene bisacetamide on growth and differentiation of cultured human malignant glioma cells

The modulation effects of hexamethylene bisacetamide (HMBA), a differentiation-inducing agent, on growth and differentiation of cells from human malignant glioma cell line SHG-44 were studied. At cytostatic doses (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 15 days), HMBA exerted a marked inhibitory effect on cell proliferation. Exposure to HMBA (5 mM and 10 mM for 12 days) also resulted in an accumulation of cells in G0/G1 phase and a decrease of cells in S phase as analyzed by flow cytometry. The reversible effects of 7.5 mM HMBA and 10 mM HMBA on cell proliferation and 10 mM HMBA on disruption of cell cycle distribution were observed when HMBA was removed from culture media on Day 6 and replaced with HMBA-free media. Colony-forming efficiency (CFE) in soft agar was remarkably decreased by HMBA (2.5 mM, 5 mM, 7.5 mM, and 10 mM for 14 days), and in 7.5 mM HMBA- and 10 nM HMBA treated cells, the CFEs were reduced to 25% and 12.5%, respectively, of that in untreated cells. Cells treated with HMBA (5 mM and 10 mM for 15 days) remained tumorigenic in athymic nude mice, but the growth rates of the xenografts were much slower than those in the control group. The effects of HMBA on cell proliferation, cell cycle distribution, CFE, and growth of xenografts were dose dependent. A more mature phenotype was confirmed by the morphological changes from spindle shape to large polygonal stellate shape and remarkably elevated expression of glial fibrillary acidic protein in cells exposed to HMBA (5 mM, 10 mM for 15 days). Our results showed that a more differentiated phenotype with marked growth arrest was induced in SHG-44 cells by HMBA.