Borbála Vincze

New derivatives of GnRH as potential anticancer therapeutic agents

GnRH (gonadotropin-releasing hormone), a decapeptide produced by the hypothalamus, plays an important role in the reproduction by regulating the pituitary-gonadal axis. Continuous high doses of GnRH or its superactive agonists result in desensitization of the pituitary gonadotropes and a suppression of sex steroid production by the gonads (chemical castration). Based on these effects, the treatment with GnRH agonists has become a widely used hormonal therapy of the sex-steroid dependent tumors. It was also demonstrated that most tumor cells contain GnRH receptors, and the direct antiproliferative effect of GnRH analogs on cancer cells might be mediated by these receptors. Development of new GnRH derivatives is focused on the decrease of their hormonal potency resulting in higher selectivity of the antitumor activity. One of the most promising natural GnRH analogs, lamprey (l) lGnRH-III, was isolated from see lamprey. This variant of GnRH binds to GnRH receptors and inhibits proliferation of various cancer cells. However, its endocrine effect is insignificant in mammals. lGnRH-III dimers and conjugates were prepared and were shown to have increased antiproliferative effects on various cancer cells, while their hormonal activity was lower than that of the native hormone. lGnRH-III was applied as targeting moiety to deliver anticancer agents to tumor cells. Research data concerning lGnRH-III and its analogs represent a new outlook for research trends of the application of GnRH compounds in cancer chemotherapy. Studies on the effects of lGnRH-III derivatives including antiproliferative effects, cytotoxicity, hormonal actions, and enzymatic stability are reviewed in this article.

Establishment, characterization and drug sensitivity of a new anaplastic thyroid carcinoma cell line (BHT-101)

SummaryA thyroid carcinoma cell line, BHT-101, has been established in vitro from a metastatic lymph node deposit in a female patient with a non-hormone producing anaplastic, partly thyroglobulin-and thyroxine (T4)-positive papillary thyroid cancer. The cell population is heterogeneous, containing epithelial-like and fibroblast-like cells, and has a doubling time of 24 h. The cell line is polyploid with hypertetraploid predominance and the karyotype showed trisomies, tetrasomies, pentasomies as well as many marker chromosomes. The majority of the cells are negative or weakly positive for thyroglobulin and thyroxine and estrogen and progesterone receptors are present in the cells. BHT-101 cells produce tumours when injected into immunosuppressed CBA/Ca mice. The cells are sensitive to adriamycin, methotrexate and tamoxifen but not to methimazole (Favistan). The epithelial-like clone 1 and the fibroblastlike clone 3, isolated from the parental line, differed in drug sensitivity. This new cell line is suitable for studying the biology of thyroid carcinoma and for parallel in vivo and in vitro studies of drug activity against thyroid cancer.

Influence of toremifene on the endocrine regulation in breast cancer patients.

In a combined phase I-II study, the hormonal effects of toremifene (TOR) were investigated in 30 patients. Half of the patients received continuous therapy of TOR 60 mg and half 300 mg of TOR orally daily. Serum concentrations of oestradiol (E2), progesterone (PROG), testosterone (TE), follicle stimulating hormone (FSH), luteinising hormone (LH), prolactin (PRL), human growth hormone (hGH) and sex hormone binding globulin (SHBG) were monitored prior to the treatment and at the second, sixth, eighth and twelfth weeks. The influence of TOR upon the hypothalamo-hypophyseal axis was investigated by the TRH (thyroid-stimulating hormone releasing hormone) functional test using 400 micrograms intravenous injection of TRH for stimulation of PRL secretion. The concentration of E2 decreased during the TOR therapy with 60 mg and 300 mg causing 82 and 71% decreases, respectively (non-significant). PRL was significantly (P < 0.001) suppressed. Both these effects reflect the anti-oestrogenic action of TOR. SHBG increased significantly at both doses of TOR, probably due to a direct oestrogen-like effect of TOR in the liver. TE decreased as a consequence of the elevated SHBG. The TRH-induced PRL release was suppressed by both doses of TOR. There were 17 and 27% reductions at 12 weeks in the 60 and 300 mg groups, respectively. Other hormones measured were not significantly affected by TOR. The hormonal effects of 60 and 300 mg doses of TOR did not differ significantly. Anti-oestrogenic (i.e. decrease of E2), and partially oestrogenic (i.e. increase of SHBG) properties as well as the antiprolactinic effects of TOR may have an overall beneficial effect in the clinical management of breast cancer patients.

Structure–activity study on the LH- and FSH-releasing and anticancer effects of gonadotropin-releasing hormone (GnRH)-III analogs

UNLABELLED GnRH-III was reported to have selective FSH-releasing activity in rats and significant anticancer potency on human breast cancer cells. To improve either of these effects, 14 analogs were synthesized and investigated for FSH/LH stimulation and breast cancer inhibition. Analogs with single amino acid changes in positions 5-7 or 10 showed small or no difference in the FSH- or LH-releasing activity compared with GnRH-III but their anticancer potency decreased significantly. Modification of the terminal amino acids, side chain cyclization at the 6-8 regions, or combined amino acid changes at positions 4, 6 and/or 8 resulted in the decrease of both effects. Gonadotropin-releasing activity of Arg(8)-GnRH-III was improved 3-11-fold. A copolymer conjugate of GnRH-III showed 2-3-fold anticancer activity while losing endocrine potency. CONCLUSION The activation of GnRH-receptors on pituitary and breast cancer cells requires a specific structure and/or conformation that makes possible to improve the anticancer selectivity of GnRH analogs.

Structure, enzymatic stability and antitumor activity of sea lamprey GnRH-III and its dimer derivatives.

Direct antitumor activity of sea lamprey (Petromyzon marinus) gonadotropin-releasing hormone III (Glp-His-Trp-Ser-His-Asp-Trp-Lys-Pro-Gly-NH(2); lGnRH-III) was described on several tumor cells. To improve the selectivity of antitumor effects without increasing the hormone releasing activity and to enhance the enzymatic stability, lGnRH-III dimers were prepared via disulfide bond formation. Our results demonstrate that the lGnRH-III dimer derivatives exhibited higher antiproliferative effect and enzymatic stability in comparison with the native lGnRH-III, while lower LH-releasing potency was determined. In order to find a correlation between the biological and structural features of these compounds, the conformation of lGnRH-III and its dimer derivatives was determined by ECD, VCD, FT-IR and (1)H NMR.

Antitumour effect of a gonadotropin-releasing-hormone antagonist (MI-1544) and its conjugate on human breast cancer cells and their xenografts

Our gonadotropin-releasing hormone (GnRH) antagonist analogue MI-1544 ([Ac-d-Trp1,3,d-Cpa2,d-Lys6,d-Ala10]GnRH) was developed as a potential contraceptive material, because it decreased the luteinizing hormone level without unfavourable side-effects. The antagonist was covalently bound to poly[Lys-(Ac-Glu0.96-dl-Ala3.1)] (AcEAK) —a branched polypeptide having a polylysine backbone — resulting in a MI-1544-AcEAK conjugate. According to our in vitro experiments the MI-1544 induced a 33%–35% decrease in cell numbers of MCF-7 and MDA-MB-231 human breast cancer cell lines at a dose of 30 μM. The biodegradable polymeric carrier, AcEAK, alone inhibited cell proliferation by only 13%–15%, while the MI-1544-AcEAK conjugate, applied at the same dose, was capable of producing 45%–50% inhibition of cell proliferation. Our in vivo experiments using immunosuppressed mice showed that MI-1544, applied twice daily s.c., inhibited the growth of oestrogensensitive and-insensitive xenografts by 65% and 30% respectively. This effect was potentiated (70%) in both types of xenografts by the presence of the polymeric carrier in the conjugate; however, the carrier by itself did not cause tumour growth inhibition. The polymeric polypeptide carrier is supposed to increase the stability of the GnRH antagonist and to prevent the rapid excretion of the covalently bound peptide molecule. The antagonist and its conjugate may have various direct and indirect effects on breast cancer cells and, as a consequence, the new GnRH antagonist conjugates are suitable for treating an extended range of breast cancers.

In-vivo antitumour effect of daunorubicin-GnRH-III derivative conjugates on colon carcinoma-bearing mice.

Targeted cancer chemotherapy is a novel approach developed for the specific delivery of anticancer drugs. Tumour targeting can be achieved by combining a chemotherapeutic agent with a targeting moiety that recognizes tumour-specific or highly expressed receptors on cancer cells. We used the gonadotropin-releasing hormone-III (GnRH-III) as a targeting moiety to which the chemotherapeutic agent daunorubicin (Dau) was attached through an oxime bond either directly or by inserting a GFLG tetrapeptide spacer. The in-vivo toxicity of Dau–GnRH-III derivative conjugates was evaluated on healthy BDF-1 female mice, and their tumour growth inhibitory effect was determined on C26 murine and HT-29 human colon carcinoma-bearing mice. Both oxime bond-containing conjugates were well tolerated and exerted significant antitumour activity on C26 colon carcinoma-bearing mice at a dose of 30 mg Dau content in conjugate/kg body weight. Furthermore, the conjugates inhibited the tumour growth more than the free drug at a dose that was still not toxic. Similar tumour growth inhibitory effects were obtained on HT-29 human colon carcinoma-bearing mice using three treatments with 15 mg Dau content in conjugate/kg. The tumour growth inhibitions according to the tumour volume and the tumour weight were 44/41% and 58/50%, respectively. Considering the results, both of the investigated Dau–GnRH-III derivative conjugates were well tolerated and had significant antitumour effect on colon carcinoma-bearing mice.

Postoperative Thyroglobulin Level Determination to Follow Up Patients with Highly Differentiated Thyroid Cancer

The highly differentiated thyroid tumours account for 0.80% of all human malignancies. The papillary and follicular tumour tissues of this tumour type are relatively benign, hormone-dependent and beside their treatment specificity they secrete the tumour-specific thyroglobulin. This it becomes possible to follow the development of metastases, the effectiveness of therapy applied as well as the history of the disease. The authors studied the change of thyroglobulin level in 153 patients with highly differentiated thyroid cancer. In 29 of 32 metastatic patients a pathologically elevated (70-100 ng/ml) thyroglobulin level was observed. This proves the 91% specificity of the method in verified metastatic tumours. Compared to the total body scintigraphy 3 false-negative and 6 false-positive cases were found. The authors establish that, irrespective of the site of metastasis, the thyroglobulin level is higher in the follicular than in the papillary subtype. It is concluded that the measurement of the serum thyroglobulin level is a suitable marker of the highly differentiated thyroid cancer since it indicates local recurrence or distant metastases by a significant increase while therapy-resultant tumour diminution is accompanied by a marked decrease.

Increase of hypophyseal hormone levels in male head and neck cancer patients

Head and neck squamous cell carcinoma (HNSCC) develops in at least 80% of cases in men with a history of smoking and heavy alcohol consumption, still it is only diagnosed in a small proportion of alcoholics. Endocrine milieu is an important factor in carcinogenesis and prognosis of several cancer types. The aim of our study was to investigate sex steroid and hypophyseal hormone status of male HNSCC patients in comparison to healthy volunteers and to patients with alcoholic liver disease, to determine possible hormonal alterations characteristic of cancer. Liver function (GGT level), and serum levels of gonadotropic hormones (FSH, LH, prolactin), sex steroids (estradiol, progesterone, testosterone) and sex hormone-binding globulin (SHBG) were compared in 130 male HNSCC patients, 54 patients with alcoholic liver disease but no known cancer, and 56 healthy controls. We found abnormal values of liver function in both HNSCC patients and alcoholics compared to healthy controls, suggesting the presence of alcoholic liver disease in the former group as well. On the other hand, a significant elevation in the level of DHEA, FSH and LH was observed in cancer patients exclusively. As a conclusion, abnormal alterations in sex steroid hormone levels can frequently be found in HNSCC patients, which may be caused in part by the alcoholic liver damage accompanying the disease. The significant increase in FSH and LH serum levels, observed only in the cancer patients, indicates that these hormones may play a role in the development and/or progression of HNSCC.

Synthesis of New Poly(N-Vinyl Pyrrolidone-Co-Maleic Acid) Peptide Hormone Conjugates with Anticancer Activity

Gonadotropin releasing hormone (GnRH) is a decapeptide regulating the gonadotropin release in organisms. Its analogues inhibit breast, endometrium and prostatic tumor cell proliferation in vitro. Some analogues were conjugated via the lysine side chain to poly(N-vinyl pyrrolidone-co-maleic acid) using biodegradable and non-biodegradable oligopeptide spacers. The conjugates were prepared by acylation of oligopeptide nitrophenyl esters with the polymeric precursor, poly(N-vinyl pyrrolidone-co-maleic anhydride), by reacting the GnRH analogues with the polymeric active ester. In vitro tests of these products exhibited increased effects on MCF-7 and MDA MB-231 breast, Ishikawa endometrium and PC3 prostatic human tumor cells compared with the parent decapeptides.