Growth hormone-releasing hormone: an autocrine growth factor for small cell lung carcinoma

Antagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of various cancers in vivo. This effect is thought to be exerted through suppression of the pituitary growth hormone-hepatic insulin-like growth factor I (IGF-I) axis and direct inhibition of autocrine/paracrine production of IGF-I and -II in tumors. However, other evidence points to a direct effect of GHRH antagonists on tumor growth that may not implicate IGFs, although an involvement of GHRH in the proliferation of cancer cells has not yet been established. In the present study we investigated whether GHRH can function as an autocrine/paracrine growth factor in small cell lung carcinoma (SCLC). H-69 and H-510A SCLC lines cultured in vitro express mRNA for GHRH, which apparently is translated into peptide GHRH and then secreted by the cells, as shown by the detection of GHRH-like immunoreactivity in conditioned media from the cells cultured in vitro. In addition, the levels of GHRH-like immunoreactivity in serum from nude mice bearing H-69 xenografts were higher than in tumor-free mice. GHRH(1-29)NH(2) stimulated the proliferation of H-69 and H-510A SCLCs in vitro, and GHRH antagonist JV-1-36 inhibited it. JV-1-36 administered s.c. into nude mice bearing xenografts of H-69 SCLC reduced significantly (P < 0.05) tumor volume and weight, after 31 days of therapy, as compared with controls. Collectively, our results suggest that GHRH can function as an autocrine growth factor in SCLCs. Treatment with antagonistic analogs of GHRH may offer a new approach to the treatment of SCLC and other cancers.

Inhibition of growth of human malignant glioblastoma in nude mice by antagonists of bombesin/gastrin-releasing peptide

The effects of antagonists of bombesin/gastrin-releasing peptide (GRP) on the growth of human malignant glioblastoma cell line U-87MG xenografted into nude mice were evaluated. Nude mice bearing s.c. implanted U-87MG tumors were treated with bombesin/GRP antagonists RC-3095 and RC-3940-II. RC-3095 and RC-3940-II administered s.c. at a dose of 20 micrograms/day for 4 weeks decreased the volume of U-87MG xenografts by 60 and 74%, respectively, compared with controls. RT-PCR analysis showed that U-87MG xenografts expressed mRNA for bombesin receptor subtype (BRS)-1 (GRP receptor) and BRS-2 (neuromedin-B receptor), but the mRNA for GRP ligand was not detected in U-87MG cells suggesting that GRP may stimulate the growth of U-87MG glioblastomas by a paracrine mechanism. The levels of mRNA for c-fos oncogene were decreased by 30-40% in U-87MG tumors treated with RC-3095 or RC-3940-II. In U-373MG glioblastoma cells, which also express BRS-1, and U-87MG cells, cultured in vitro, GRP(14-27) induced the expression of c-fos mRNA, and some c-jun mRNA, in a time-dependent manner with the maximal effect occurring 2 h after the stimulation and a return to basal levels after 8 h. Antagonist RC-3940-II inhibited the stimulation of c-fos by GRP(14-27). Our results indicate that antagonists of bombesin/GRP inhibit the growth of U-87MG glioblastomas by a mechanism that may involve the downregulation of c-fos oncogene.

Targeted cytotoxic analogue of bombesin/gastrin-releasing peptide inhibits the growth of H-69 human small-cell lung carcinoma in nude mice

Recently, we developed a powerful cytotoxic analogue of bombesin AN-215, in which the bombesin-like carrier peptide Gln-Trp-Ala-Val-Gly-His-Leu-psi(CH2-NH)-Leu-NH2 (RC-3094) is conjugated to a potent derivative of doxorubicin, 2-pyrrolinodoxorubicin (AN-201). Small-cell lung carcinomas (SCLCs) are known to express high levels of bombesin receptors. We evaluated whether these receptors could be used for targeting cytotoxic bombesin analogue to H-69 SCLC cells. H-69 cells were xenografted into male nude mice, which then received an intravenous injection of AN-215, cytotoxic radical AN-201, the carrier peptide RC-3094 alone or unconjugated mixture of RC-3094 and AN-201. The levels of mRNA for bombesin receptor subtypes were evaluated by reverse transcription-polymerase chain reaction. In vitro, both the analogue AN-215 and the radical AN-201 showed strong antiproliferative effects on H-69 cells, AN-215 requiring more time to exert its action at 10(-8) M concentration than AN-201. In vivo, the growth of H-69 SCLC tumours was significantly inhibited by the treatment with 200 nmol kg(-1) of AN-215, while equimolar doses of the cytotoxic radical AN-201 or the mixture of AN-201 and the carrier peptide were toxic and produced only a minor tumour inhibition as compared with control groups. mRNA for bombesin receptor subtypes 2 (BRS-2) and 3 (BRS-3) was detected in H-69 tumours. The mRNA levels for BRS-3, but not for BRS-2, were lower in the AN-215-treated tumours as compared with controls. Our results demonstrate that the cytotoxic bombesin analogue AN-215 could be considered for targeted therapy of tumours, such as SCLC, that express bombesin receptors.

Inhibition of growth, production of insulin-like growth factor-II (IGF-II), and expression of IGF-II mRNA of human cancer cell lines by antagonistic analogs of growth hormone-releasing hormone in vitro

Antagonistic analogs of growth hormone-releasing hormone (GHRH) suppress growth of various tumors in vivo. This effect is exerted in part through inhibition of the GHRH-GH-insulin-like growth factor (IGF)-I axis. Nevertheless, because autocrine/paracrine control of proliferation by IGF-II also is a major factor in many tumors, the interference with this growth-stimulating pathway would offer another approach to tumor control. We thus investigated whether GHRH antagonists MZ-4-71 and MZ-5-156 also act on the tumor cells directly by blocking the production of IGF-II. An increase in the IGF-II concentration in the media during culture was found in 13 of 26 human cancer cell lines tested. Reverse transcription-PCR studies on 8 of these cell lines showed that they also expressed IGF-II mRNA. Antagonists of GHRH significantly inhibited the rate of proliferation of mammary (MDA-MB-468 and ZR-75-1), prostatic (PC-3 and DU-145), and pancreatic (MiaPaCa-2, SW-1990, and Capan-2) cancer cell lines as shown by colorimetric and [3H]thymidine incorporation tests and reduced the expression of IGF-II mRNA in the cells and the concentration of IGF-II secreted into the culture medium. Growth and IGF-II production of lung (H-23 and H-69) and ovarian (OV-1063) cancer cells that express mRNA for IGF-II and excrete large quantities of IGF-II also was marginally suppressed by the antagonists. These findings suggest that antagonistic analogs of GHRH can inhibit growth of certain tumors not only by inhibiting the GHRH-GH-IGF-I axis, but also by reducing the IGF-II production and by interfering with the autocrine regulatory pathway.

Decrease in telomerase activity in U-87MG human glioblastomas after treatment with an antagonist of growth hormone-releasing hormone

Antagonists of growth hormone-releasing hormone (GH-RH) inhibit the growth of various tumors through mechanisms that involve the suppression of the insulin-like growth factor I and/or insulin-like growth factor II levels or secretion. In the present study, we tested the hypothesis that the tumor inhibition is associated with a decrease in telomerase activity because telomerase is considered obligatory for continued tumor growth. Nude mice bearing xenografts of U-87MG human glioblastomas were treated with GH-RH antagonist MZ-5-156. Telomerase activity was assessed by the telomerase repeat amplification protocol. Treatment with MZ-5-156 reduced levels of telomerase activity as compared with controls. When U-87 glioblastomas, H-69 small cell lung carcinomas, H-23 non-small cell lung carcinomas, and MDA-MB-468 breast carcinoma cells were cultured in vitro, addition of 3 microM MZ-5-156 also inhibited telomerase activity. Reverse transcription-PCR analysis revealed that in U-87MG glioblastomas, the expression of the hTRT gene encoding for the telomerase catalytic subunit was significantly decreased by MZ-5-156, whereas the levels of mRNA for hTR and TP1, which encode for the telomerase RNA and telomerase-associated protein, respectively, were unaffected. The repression of the telomerase activity was not accompanied by a significant decrease of mRNA level for the c-myc protooncogene that regulates telomerase. Our findings suggest that tumor inhibition induced by the GH-RH antagonists in U-87MG glioblastomas is associated with the down-regulation of the hTRT gene, resulting in a decrease in telomerase activity. Further studies are needed to establish whether GH-RH antagonists produce telomerase inhibition in other tumors.

Microsatellite instability and loss of heterozygosity in human pterygia

AIMS/BACKGROUND

Pterygium is a common benign lesion of the corneoconjunctival limbus. Although environmental factors, such as ultraviolet irradiation, have been suggested as the main causative factor in the development of the disease, however, the aetiopathology of pterygium remains obscure. In this study the possibility of detecting genetic alterations in the microsatellite DNA of the pterygium was investigated.

METHODS

Fifteen specimens were assessed for for loss of heterozygosity (LOH) and microsatellite instability (MI) by seven microsatellite markers on four chromosomal arms.

RESULTS

Nine (60%) pterygia exhibited genetic alterations. Eight specimens (53%) exhibited LOH, while two specimens (13%) MI in at least one marker. 17q11.2-q21 is a commonly deleted region, as the frequency of LOH at this region is significantly high (47%).

CONCLUSION

This finding indicates the existence of tumour suppressor genes in this region implicated in the disease without excluding the presence of other tumour suppressor genes in the other chromosomal regions that were examined. MI was apparent in only a few specimens but it is indeed a detectable phenomenon, suggesting that decreased fidelity in DNA replication and repair may be associated with the development of pterygium. Detection of LOH and MI, two events taking place in tumour cells or in premalignant cells, constitutes strong evidence that there must be transformed cells in the pterygial tissue and it should be considered to be a neoplastic benign lesion.

Microsatellite instability and loss of heterozygosity in primary breast tumours

Allelic imbalance or loss of heterozygosity (LOH) studies have been used extensively to identify regions on chromosomes that may contain putative tumour suppressor genes. We looked for evidence of microsatellite instability (MI) and LOH on chromosome 7q, 10q, 11p and 17q using seven polymorphic microsatellite markers. In 42 paired breast cancer-peripheral blood DNA samples we identified 24 tumours (57%) exhibiting genetic alterations. Twenty-one specimens exhibited LOH (50%), while 11 specimens exhibited MI (26%) in at least one microsatellite marker. The most frequent incidence of LOH was found for the marker THRA1 (8/33, 24%) indicating that thra I gene becomes a strong candidate tumour suppressor gene, whereas of MI it was D10S109 (3/26, 12%). These MI and LOH data were analysed using a range of clinicopathological parameters. Tumours displaying MI with no evidence of LOH and tumours exhibiting MI and LOH belonging to stage II or III were found, however none were at stage I. These data suggest that MI may be an early event in mammary tumorigenesis whereas LOH occurs at a late stage. A significant association between the absence of oestrogen receptors (p < 0.01) and the absence of both oestrogen and progesterone receptors (p < 0.001) at 17q21 were observed, indicating a possible relationship between specific genetic changes at this region and hormonal deregulation in the progression of breast cancer.

Mutations and expression of the ras family genes in leukemias

The levels of expression and the incidence of codon 12 point mutations of the ras family genes were studied in 18 cases of leukemia, seven with acute myeloblastic leukemia (AML), three with acute lymphoblastic leukemia (ALL), four cases with chronic myelogenic leukemia (CML) and four cases with chronic lymphocytic leukemia (CLL). Elevated expression of the ras genes was found for 39%, 61% and 67% of the specimens for the H-ras, K-ras and N-ras, respectively. A trend was found between the overexpression of the N-ras gene and the acute leukemias: all 10 acute leukemias exhibited overexpression of the N-ras gene, while only two of the CML cases, both in blastic crisis, showed elevated levels of the N-ras gene. Codon 12 point mutations at the N-ras gene were found in two of seven cases (28%) with AML and one of four cases (25%) with CML. The only K-ras codon 12 point mutation was found in a patient with CLL. No mutations were found in the codon 12 of H-ras. Our data suggest that apart from the point mutations, overexpression of the ras family genes is important in the development of the disease.

Transcriptional activation of H-ras, K-ras and N-ras proto-oncogenes in human bladder tumors

In this study we demonstrate the involvement of ras oncogenes in bladder cancer at the level of RNA overexpression. We examined 26 bladder specimens, consisting of paired tumor and adjacent normal tissue and found that H-ras transcripts were overexpressed in 39% of the specimens while K-ras and N-ras in 58% of total specimens. Each tumor specimen had a unique pattern of overexpression for the three ras genes. A competitive-RT-PCR was employed for H-ras and a beta-actin control gene was co-amplified with K-ras or N-ras genes. These results indicate that the involvement of ras oncogenes in bladder cancer could be relative to overexpression of these genes.

Instability at the H-ras minisatellite in human atherosclerotic plaques

The development of atherosclerotic plaques is characterised by the accumulation of lipids and the proliferation of smooth muscle cells. At the subcellular level, the abnormal expression of cytokines and growth factors, as well as the presence of transforming oncogenes, has been recognised and associated with the disease. The aim of the present study was to investigate whether instability at a minisatellite region located downstream of the H-ras proto-oncogene possessing enhancer activity, is a detectable phenomenon in atherosclerotic plaques. Thirty specimens were analysed by polymerase chain reaction (PCR) in order to reveal alterations of the repetition number and by restriction fragment length polymorphism (RFLP) with BstNI restriction endonuclease for the detection of point mutations within the 28 bp core repetitive element. No point mutations were found among the 30 cases tested; however, alterations of the repetition number of the core were detected in 5 (17%) cases. Our results suggest that instability at the H-ras minisatellite may be associated with development of the disease.

Loss of heterozygosity and microsatellite instability in human atherosclerotic plaques

Several lines of evidence suggest that mutation events may be involved in the development of atherosclerosis. The aim of the present investigation was to perform an allelotype analysis in 30 atherosclerotic lesions in order to reveal any deletions involved in the development of the disease. Eighteen chromosomal arms were tested by one microsatellite marker located on each arm and allelic imbalance in at least one marker was observed in 7 (23%) cases. Furthermore, the analysis revealed the presence of microsatellite instability (MI) in 10 (33%) cases, suggesting that an increase in the mutation rate may be involved in the formation of the plaque. These results highlight the mutation concept for the atherogenesis and suggest that LOH and MI may be involved in the development of the disease.

Quantitation of the allelic imbalance provides evidence on tumour heterogeneity: a hypothesis

The observation of loss of heterozygosity (LOH) in tumours represents a useful clue to the presence of tumour suppressor genes (TSGs). However, analysis of this phenomenon is often complicated by tumour heterogeneity and the presence of DNA from adjacent normal tissues. The present study suggests a quantitative approach for measurement of LOH which may help to distinguish between these possibilities and to provide clues for the heterogeneous process of tumour progression. We applied this methodology to a laryngeal tumour with LOH at markers D9S171, D9S157, D8S87 and THRA1 and found that LOH at D9S171 is the commonest aberration among the tumour cells, while LOH at the THRA1 marker is present in only a small subset of the tumour cells. It is likely that LOH at D9S171 occurs early uin tumour development while LOH at the rest of the markers tested occurred later resulting in the generation of heterogeneous cell populations.

Microsatellite instability in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a relatively common disease, affecting mainly males in the western world. Although substantial data are available as regards the clinicopathological characterization of COPD, little is known of the molecular basis of the disease. In the present study we analysed the incidence of microsatellite instability (MI) in cytological specimens from patients with COPD. MI reflects increased mutational rate and is associated with decreased accuracy in the DNA repair, resulting in the accumulation of somatic mutations in cells manifesting this genetic alteration. Among 31 specimens tested, 7 (23%) exhibited MI in at least one among 6 microsatellite markers tested. 5 cases were affected in only one marker while the remaining two cases exhibited evidence of MI in two microsatellite markers. These data suggest that an elevated mutational rate as reflected by the increased incidence of MI is associated with the development of the disease.

Microsatellite instability in human atherosclerotic plaques

The aetiopathology of atherosclerosis remains obscure. Although histologically the accumulation of lipids and the proliferation of the smooth muscle cells represents the main feature of the disease, little is known as regards the molecular alterations associated with the atherosclerotic lesions. In the present study we investigated whether an elevated mutational rate is detectable in human atheromatous plaques. Thirty specimens were assessed for microsatellite instability (MI) by 7 microsatellite markers and MI, in at least one marker, was apparent in 6 (20%) cases. Our data suggest that decreased fidelity in DNA replication and repair may be associated with the development of the disease.

Detection of herpesvirus-like DNA sequences in Mediterranean Kaposi's sarcoma

The aetiology of Kaposi's sarcoma remains obscure, however, epidemiological studies indicate that the disease possesses an infectious aetiology. Recent data revealed the presence of specific herpesvirus-like DNA sequences (KHSV) in all forms of Kaposi's sarcoma indicating that a novel virus may be the infectious agent which causes the disease. The aim of the present investigation was to assess the incidence of this herpesvirus-like DNA sequence in 28 Mediterranean Kaposi's sarcomas. DNA was extracted from formalin-fixed paraffin-embedded tissues and analysed by a sensitive PCR based assay. The KSHV specific DNA sequences were found in 22 of 28 (79%) cases suggesting a potential important role in the development of the disease.

Allelotype of squamous cell carcinoma of the head and neck: fractional allele loss correlates with survival

Allelic imbalance or loss of heterozygosity (LOH) studies have been used extensively to identify regions on chromosomes that may contain putative tumour-suppressor genes. We have undertaken an extensive allelotype of 80 specimens of squamous cell carcinoma of the head and neck (SCCHN) using 145 polymorphic microsatellite markers on 39 chromosome arms. Allelic imbalances were found most frequently on chromosome arms 3p, 9p, 17p and 18q with over 45% LOH and imbalances on 1p, 1q, 2p, 5q, 6p, 6q, 8p, 8q, 9q, 11q, 13q, 17q and 19q were found in more than 20% of SCCHN. These LOH data were analysed against a range of clinicopathological parameters which included previously untreated and previously treated tumours; correlations were found between LOH on 9q and nodes at pathology (P = 0.02) and between histopathological grade and LOH on 12q (P = 0.02) and 13q (P = 0.01). In the group of previously untreated tumours, a correlation was found between site of tumour and LOH on 3p (P = 0.019), and 8p (P = 0.029), while TNM staging correlated with LOH on 3p (P = 0.019) and 17p (P = 0.016). Fractional allele loss (FAL) was calculated for 52 tumours with LOH data on nine or more chromosomal arms and found to have a median value of 0.22 (range 0.0-0.80). Correlations were found between FAL > median value and nodes at pathology (P = 0.01) and tumour grade (P = 0.06), demonstrating that advanced tumours with lymph node metastasis often had LOH at multiple sites. FAL > median value was found to correlate with a poor survival (P < 0.03) and, furthermore, FAL > median value correlated with poor survival in the previously untreated patients (P < 0.019). These results indicate that assessment of the accumulation of genetic damage, as provided by allelotype data, provides a useful molecular indicator of the tumour behaviour and clinical outcome.

Loss of heterozygosity at 9p and 17q in human laryngeal tumors

Recent investigations revealed that the 9p arm and 17q arm of human chromosomes harbour tumour suppressor genes (TSGs) with an important role in multistage carcinogenesis. At the 9p arm is located the p16 (MTS1) TSG and probably others with an effect on various human tumours such as acute lymphoblastic leukaemia, bladder cancer, gliomas, malignant mesotheliomas, melanomas and non-small cell lung carcinomas. In addition, the 17q arm harbours BRCA1 TSG which is responsible for approximately 80% of the familial breast/ovarian cancer cases. In order to investigate the implication of these performed a loss of heterozygosity (LOH) analysis with 10 polymorphic microsatellite markers (three at the 17q arm surrounding the BRCA1 region and seven at the 9p arm). Fourteen of the 17 (82%) tumours exhibited deletions at 9p. The highest incidence of LOH (6/13, 46%) was found for the marker D9S157 at 9p22. One sample exhibited deletion of all the informative markers tested indicating deletion of the complete 9p arm. No homozygous deletions were found. LOH at the 17q arm near the BRCA1 locus was found in 6 (35%) among 17 specimens. The results of this study indicate that allelic deletions at 9p are frequent in the development of laryngeal tumours. The highest incidence of LOH was found for the marker D9S157 which is near, but distinct from the location of p16 (MTS1) tumour suppressor gene, indicating the presence of multiple tumour suppressor genes within this chromosomal region. In addition, BRCA1 TSG is implicated in the development of laryngeal tumours.

Instability at the H-ras minisatellite is associated with the spontaneous abortion of the embryo

Recently we have shown that microsatellite instability (MI) is a detectable phenomenon in aborted embryonic tissues. In the present study we investigated if instability is also detectable in a minisatellite located at the 3'-end of the H-ras proto-oncogene, affecting either the repetition number of the 28-bp core generating larger or smaller alleles or its sequence creating a detectable restriction fragment length polymorphism (RFLP). Among 30 aborted embryonic tissues, alterations at the repetition number of the core were found in 3 (10%) while point mutations were detected in 7 (23%) cases. These results indicate that structural alterations of the H-ras minisatellite may be associated with the rejection of the embryo.

Instability at microsatellite sequences in spontaneously aborted human embryos provides evidence for a novel mechanism for recurrent miscarriages

Several factors have been proposed to confer a risk for abortion of the embryo. However, the aetiology of spontaneous abortions remains unclear. In the present study we investigated if an increased mutational rate occurs in the embryonic tissue and whether this phenomenon is associated with recurrent miscarriage. The mutational rate was assessed in 30 spontaneously aborted embryos using a bank of 8 highly polymorphic microsatellite markers, each one located on a different chromosome. The microsatellite sequences of DNA extracted from distal sites of each embryo were amplified by the polymerase chain reaction and the electrophoretic patterns were compared. Shifts in the mobility of the microsatellites indicating instability were scored for 12 among 30 (40%) specimens, thus suggesting that microsatellite instability (MI) is a relatively common feature of spontaneously aborted embryonic tissues. Association was found between instability and the absence of normal childbirth: 11 among 18 cases without a normal childbirth exhibited evidence of MI while only one among 12 cases with normal childbirth was positive for MI. Our results suggest that instability at microsatellite sequences which indicate decreased fidelity in DNA replication and repair are associated with the recurrent abortion of the embryo, particularly in cases without a normal childbirth.

Mutations of ras genes in human tumors (review)

Ras family genes (H-, K- and N-ras) are implicated in a wide range of human rumours. Mutations are a major activating mechanism for the ras family genes, mainly in codons 12, 13 and 61, resulting in their conversion from proto-oncogenes to activated oncogenes. The detection of mutant ras alleles in human tumours has been performed by several investigators in a wide range of tissues. The aim of our review was to summarize the data obtained from these studies and to investigate whether the presence of mutant ras alleles was associated with particular clinical parameters.