Growth inhibition of MXT mammary carcinoma by enhancing programmed cell death (apoptosis) with analogs of LH-RH and somatostatin

BDF female mice inoculated with MXT mammary adenocarcinoma were treated for 30 days with microcapsules of the luteinizing hormone-releasing hormone (LH-RH) agonist D-Trp-6-LH-RH (releasing 25µg/day for 30 days), microcapsules of the somatostatin agonist RC-160 (liberating 25µg/day for one month), or the combination of these peptides. Bilateral surgical ovariectomy was performed in one group which served as an additional control. Tumor volume was measured weekly during the treatment period of 30 days. When tumor volume changes in the treated groups were compared to the corresponding changes in controls, the combination of D-Trp-6-LH-RH and RC-160 was the most effective in inhibiting tumor growth and approached the effect of surgical ovariectomy. At the conclusion of the experiment, tumor weights were also measured. All peptide analogs inhibited tumor weight by 42 to 63%. In the D-Trp-6-LH-RH treated group, ovarian weights and uterine weights decreased by 48% and 52%, respectively, as compared to controls. Histologically, the regressive changes in tumors caused by the treatment with RC-160, D-Trp-6-LH-RH and their combination were characterized by the coexistence of apoptosis (programmed cell death) and coagulation necrosis. The transition of apoptosis into coagulation necrosis was a common finding. The term apoptotic index is proposed for the ratio of tumorous glands containing apoptotic cells. The apoptotic index was higher in the treated groups than in the control.     

Effect of a cytotoxic analog of LH-RH (T-98) on the growth of estrogendependent MXT mouse mammary cancers: Correlations between growth characteristics and EGF receptor content of tumors

Summary Female BDF mice bearing estrogen-dependent MXT mouse mammary cancers were treated for 4 weeks with a cytotoxic analog of luteinizing hormone-releasing hormone (LH-RH), T-98 (agonist [D-Lys⁶]LH-RH linked to glutaryl-2(hydroxymethyl)anthraquinone). The effects of T-98 were compared to those of equimolar amounts of the cytotoxic moiety 2-(hydroxymethyl)anthraquinone hemiglutarate (G-HMAQ) and carrier LH-RH agonist [D-Lys⁶]LH-RH. Both T-98 and [D-Lys⁶]LH-RH significantly inhibited the growth of MXT cancers, but G-HMAQ had only a minor non-significant effect. Cytotoxic analog T-98 and the carrier [D-Lys⁶]LH-RH had similar inhibitory hormonal activities on the pituitary-gonadal axis, but T-98 caused a larger reduction in tumor volume and decreased proliferation characteristics such as mitotic activity and AgNOR numbers in tumor cells to a greater extent than the carrier. Tumor inhibition by T-98, [D-Lys⁶]LH-RH, and ovariectomy was connected with a significant decrease in binding capacity of EGF receptors in tumor cell membranes. The concentration of EGF receptors remained high in tumors that continued to enlarge in spite of treatment and in all control untreated tumors, even those of small size. Thus, the changes in EGF receptors are likely to be the result of the therapy. Treatment with T-98 caused a greater reduction in the binding capacity of EGF receptors in tumors than [D-Lys⁶]LH-RH. This could explain the higher inhibitory effect of the cytotoxic analog on tumor growth. Since radiolabeled T-98 was shown to accumulate in MXT cancers 3 hours after a subcutaneous injection, this indicates that specific targeting might play a role in the antitumor effect exerted by this cytotoxic analog.Abbreviations LH luteinizing hormone - LH-RH LH-releasing hormone - EGF epidermal growth factor - EGF-R EGF receptor - TGF transforming growth factor - NOR nucleolar organizing region - AgNOR argyrophilic NOR - G-HMAQ 2(hydroxymethyl)anthraquinone-hemiglutarate - HPLC high performance liquid chromatography - TNF tumor necrosis factor - 5-FU 5-fluorouracil - PBS phosphate-buffered saline     

Localization of human breast tumors grafted in nude mice with a monoclonal antibody directed against a defined cell surface antigen of human mammary epithelial cells

Summary A mouse monoclonal antibody (BLMRL-HMFG-Mc5) prepared against a defined cell surface antigen of human mammary epithelial cells, non-penetrating glycoprotein (NPGP), was used in imaging and distribution studies in athymic nude mice grafted with human breast tumors. Forin vivo tissue distribution studies,¹²⁵I-labeled monoclonal antibody was injected into nude mice carrying simulated metastases of human tumors (breast and colon carcinomas). After 22–24 hr the amount of radioactivity per gram of tissue was 3–4 times higher in the breast tumor than in liver, brain, lung, muscle, or spleen. In contrast, colon carcinoma tissue, grafted and treated likewise, did not show higher accumulation of radioactivity relative to other tissues. At 4 days, the incorporation in breast tumors remained almost as high, while the circulating radioactive tracer and the incorporation in tissues other than breast had fallen significantly.In tumor imaging studies, breast tumor masses as small as 4 mm in diameter were clearly localized on a whole body scan using¹³¹I-labeled BLMRL-HMFG-Mc5 antibodies with a High-Purity germanium gamma camera. Normalization of¹³¹I-distribution to that of^99mTc-pertechnetate increased the specificity of this imaging methodology. The quantitative density of¹³¹I-label was 2–3 fold higher over the breast tumor than over comparable areas of the mouse. No positive localization images were obtained for similar implants of colon and lung carcinomas or melanomas after injections of¹³¹I-labeled BLMRL-HMFG-Mc5. Localization of human breast tumors in this model can be achieved with¹³¹I-labeled anti-breast epithelial monoclonal antibodies.Abbreviations NPGP non-penetrating glycoprotein - CEA carcinoembryonic antigen     

CXCR4 peptide antagonist inhibits primary breast tumor growth,metastasis and enhances the efficacy of anti‐VEGF treatment or docetaxel in a transgenic mouse model

CXCR4 is a chemokine receptor implicated in the homing of cancer cells to target metastatic organs, which overexpress its ligand, stromal cell‐derived factor (SDF)‐1. To determine the efficacy of targeting CXCR4 on primary tumor growth and metastasis, we used a peptide inhibitor of CXCR4, CTCE‐9908, that was administered in a clinically relevant approach using a transgenic breast cancer mouse model. We first performed a dosing experiment of CTCE‐9908 in the PyMT mouse model, testing 25, 50 and 100 mg/kg versus the scrambled peptide in groups of 8–16 mice. We then combined CTCE‐9908 with docetaxel or DC101 (an anti‐VEGFR2 monoclonal antibody). We found that increasing doses of CTCE‐9908 alone slowed the rate of tumor growth, with a 45% inhibition of primary tumor growth at 3.5 weeks of treatment with 50 mg/kg of CTCE‐9908 (p = 0.005). Expression levels of VEGF were also found to be reduced by 42% with CTCE‐9908 (p = 0.01). In combination with docetaxel, CTCE‐9908 administration decreased tumor volume by 38% (p = 0.02), an effect that was greater than that observed with docetaxel alone. In combination with DC101, CTCE‐9908 also demonstrated an enhanced effect compared to DC101 alone, with a 37% decrease in primary tumor volume (p = 0.01) and a 75% reduction in distant metastasis (p = 0.009). In combination with docetaxel or an anti‐angiogenic agent, the anti‐tumor and anti‐metastatic effects of CTCE‐9908 were markedly enhanced, suggesting potentially new effective combinatorial therapeutic strategies in the treatment of breast cancer, which include targeting the SDF‐1/CXCR4 ligand/receptor pair.