Enhanced expression of neuropeptides in human breast cancer cell lines following irradiation

The RNA-binding protein Musashi 1 stabilizes the oncotachykinin 1 mRNA in breast cancer cells to promote cell growth

Substance P and its truncated receptor exert oncogenic effects. The high production of substance P in breast cancer cells (BCCs) is caused by the enhancement of tachykinin (TAC)1 translation by cytosolic factor. In vitro translational studies and mRNA stabilization analyses indicate that BCCs contain the factor needed to increase TAC1 translation and to stabilize the mRNA. Prediction of protein folding, RNA-shift analysis, and proteomic analysis identified a 40 kDa molecule that interacts with the noncoding exon 7. Western blot analysis and RNA supershift identified Musashi 1 (Msi1) as the binding protein. Ectopic expression of TAC1 in nontumorigenic breast cells (BCs) indicates that TAC1 regulates its stability by increasing Msi1. Using a reporter gene system, we showed that Msi1 competes with microRNA (miR)130a and -206 for the 3' UTR of exon 7/TAC1. In the absence of Msi1 and miR130a and -206, reporter gene activity decreased, indicating that Msi1 expression limits TAC1 expression. Tumor growth was significantly decreased when nude BALB/c mice were injected with Msi1-knockdown BCCs. In summary, the RNA-binding protein Msi1 competes with miR130a and -206 for interaction with TAC1 mRNA, to stabilize and increase its translation. Consequently, these interactions increase tumor growth.

Thalidomide and irradiation combination therapy increases substance P levels in vitro

Thalidomide is an anti-angiogenic agent that is used in the treatment of cancer. However, in many cases, particularly in patients with breast cancer, thalidomide treatment alone is insufficient and must be combined with other drugs or therapies. In the clinical setting, thalidomide is most commonly used in combination with radiation therapy. However, the exact mechanisms of its effect are unkown. Radiotherapy alters the expression of substance P, which is considered a crucial pro-angiogenic peptide. To determine whether thalidomide and radiotherapy in combination overcome the limitations of each as monotherapy, we examined the effects of the combination on the growth of breast cancer cells as well as on the expression of substance P in vitro. Mouse breast cancer cells (4T1) and cells produced from metastatic lesions (4THMpc) were treated with radiotherapy (RT) (45 Gy) alone, thalidomide (Thal) (40 μg/ml) alone or combination therapy (40 μg/ml Thal + 45 Gy RT), and compared with control cells. MTS, Live/Dead and trypan blue exclusion assays were used to evaluate the cytotoxic effects of the treatments. The levels of substance P in the conditioned media and in the cell lysates were determined by a substance P ELISA kit, and changes in the protein content were analyzed by Western blotting. Thalidomide alone resulted in a significant inhibition in the growth of the 4T1 (34.1%) and 4THMpc (52.6%) cell lines. RT alone inhibited the growth of the 4T1 (19.2%) and 4THMpc (23.31%) cell lines. The combination therapy enhanced the growth inhibition noted in the 4T1 (47.9%) and 4THMpc (62.03%) cell lines. The expression of substance P in the conditioned media and in the cell lysates increased within 72 h of RT. This increase was significantly enhanced with the combination therapy. These data indicate that thalidomide inhibits breast cancer cell growth and potentiates the anti-tumor effects of radiation at appropriate doses.

Gender-specific effects of calcitonin gene-related peptide and substance P on coronary blood flow in an experimental model

BACKGROUND

Calcitonin gene-related peptide (CGRP) and substance P (SP) play counter-regulatory roles in coronary flow. This study is to assess whether effects of CGRP and SP are gender-specific.

METHODS

Langendorff-perfused hearts were used to compare coronary flow rates among 119 wild-type, alpha-CGRP and SP receptor knockout mice under various perfusion pressures (20, 30, 40, 50 mmHg).

RESULTS

For mouse heart coronary flow rate, deletion of alpha-CGRP gene resulted in significant reduction for both genders at all pressures; female CGRP knockout showed 15.3% reduction (P < .01); male CGRP knockout showed 13.8% reduction (P < .01); no significant difference between male and female CGRP knockout; female SP receptor knockout showed 13.9% increase (P < .01); female SP receptor knockout had a greater percentage decrease than male (P < .01).

CONCLUSIONS

CGRP plays similar roles as a vasodilator in males and females. SP seems to act as a vasoconstrictor in females.

Nuclear Factor-κB Accounts for the Repressor Effects of High Stromal Cell–Derived Factor-1α Levels onTac1Expression in Nontumorigenic Breast Cells

Stromal cell-derived factor-1alpha (SDF-1alpha) is a CXC chemokine that interacts with CXCR4 receptor. Tac1 encodes peptides belonging to the tachykinins, including substance P. SDF-1alpha production is decreased in Tac1 knockdown breast cancer cells and is also reduced in these cancer cells following contact with bone marrow stroma when Tac1 expression is increased. Here, we report on the effects of relatively high and low SDF-1alpha levels on Tac1 expression in nontumorigenic breast cells MCF12A. Reporter gene assays, Northern analyses, and ELISA for substance P showed increased Tac1 expression at 20 and 50 ng/mL SDF-1alpha and reduced expression at 100 ng/mL. Omission of the untranslated region showed a dose-dependent effect of SDF-1alpha on reporter gene activity, suggesting that receptor desensitization cannot account for the suppressive effects at 100 ng/mL SDF-1alpha. Tac1 expression at high SDF-1alpha involves an intracellular signaling pathway that incorporates the activation of phosphatidylinositol 3-kinase-phosphoinositide-dependent kinase-1-AKT-nuclear factor-kappaB (NF-kappaB). The major repressive effect occurs via NF-kappaB located within exon 1. In summary, NF-kappaB is involved in the repression of Tac1 at higher levels of SDF-1alpha in MCF12A. These results are relevant to dysfunction of Tac1 in breast cancer cells and also provide insights on the behavior of breast cancer cells as they traverse across gradient changes of SDF-1alpha.

Isoform-specific activation of latent transforming growth factor beta (LTGF-beta) by reactive oxygen species

The three mammalian transforming growth factor beta (TGF-beta) isoforms are each secreted in a latent complex in which TGF-beta homodimers are non-covalently associated with homodimers of their respective pro-peptide called the latency-associated peptide (LAP). Release of TGF-beta from its LAP, called activation, is required for binding of TGF-beta to cellular receptors, making extracellular activation a critical regulatory point for TGF-beta bioavailability. Our previous work demonstrated that latent TGF-beta1 (LTGF-beta1) is efficiently activated by ionizing radiation in vivo and by reactive oxygen species (ROS) generated by Fenton chemistry in vitro. In the current study, we determined the specific ROS and protein target that render LTGF-beta1 redox sensitive. First, we compared LTGF-beta1, LTGF-beta2 and LTGF-beta3 to determine the generality of this mechanism of activation and found that redox-mediated activation is restricted to the LTGF-beta1 isoform. Next, we used scavengers to determine that ROS activation was a function of OH(.) availability, confirming oxidation as the primary mechanism. To identify which partner of the LTGF-beta1 complex was functionally modified, each was exposed to ROS and tested for the ability to form a latent complex. Exposure of TGF-beta1 did not alter its ability to associate with LAP, but exposing LAP-beta1 to ROS prohibited this phenomenon, while treatment of ROS-exposed LAP-beta1 with a mild reducing agent restored its ability to neutralize TGF-beta1 activity. Taken together, these results suggest that ROS-induced oxidation in LAP-beta1 triggers a conformational change that releases TGF-beta1. Using site-specific mutation, we identified a methionine residue at amino acid position 253 unique to LAP-beta1 as critical to ROS-mediated activation. We propose that LTGF-beta1 contains a redox switch centered at methionine 253, which allows LTGF-beta1 to act uniquely as an extracellular sensor of oxidative stress in tissues.

Technetium labeled bombesin-like peptide: preliminary report on breast cancer uptake in patients

Bombesin-like peptides are neurotransmitters and cancer growth factors. Several tumors, breast cancer among them, show one or more than one of the three known bombesin receptors. We have synthesized and labeled with technetium 99m a new pentadecapeptide, analogue to the leu13 amphibian bombesin (99mTc BN). Labeling yield was 83 +/- 4%. Prone Scintimammography was performed on five patients affected by breast cancers (T categorization: two T1b and three T1c), after injecting 0.7 mg, 185 to 296 MBq (5 to 8 mCi) of the peptide. Total body scan did not show free technetium biodistribution. No adverse reaction was observed. Prone Scintimammography with 99mTc Sestamibi (99mTc SM) was also performed few days later. 99mTc BN detected all 5 cancers, whereas 99mTc SM only four: all the T1c and one T1b cancer. Two of them showed axillary node invasion that was detected by both the radiotracers. A fibroadenoma present on contralateral breast to the one with cancer, was not detected neither by 99mTc SM nor by 99mTc BN. Tumor/breast normal tissue ratio (T/B) was constantly higher with 99mTc BN than with 99mTc SM. Maximal T/B was measured as 1.79 with 99mTc SM and 2.25 with 99mTc BN 5 min after fast i.v. administration. In conclusion our 99mTc BN is taken up by primary breast cancer showing higher T/B than 99mTc SM (p < 0.01). In our limited scale, 99mTc BN appears to be safe and, in our limited scale, even more accurate than 99mTc SM for detecting breast cancer.

Rapid induction of long-lasting drug efflux activity in brain vascular endothelial cells but not malignant glioma following irradiation

The influence of radiotherapy on malignant glioma multidrug resistance to chemotherapy was evaluated because patients with glioma often are treated with a combination of radiotherapy and chemotherapy. Multidrug resistance gene (MDR1, mdr1a, and mdr1b) transcripts were found in human and rat glioma cell lines. P-Glycoprotein (Pgp) was immunohistochemically detected in glioma cell lines and in the rat brain vascular endothelial cell line (RBE4). A multidrug resistance pump efflux activity assay demonstrated increased calcein efflux of RBE4 endothelial cells, but not glioma cells, 2 h after irradiation and still increased 14 d after irradiation. The increased efflux was equally inhibited by verapamil with or without irradiation. In the rat intracranial glioma model (BT4C), Pgp was demonstrated in capillary endothelial cells of the tumor tissue and surrounding normal brain, but not in tumor cells. The expression of gene transcripts or Pgp was not affected by irradiation. The results indicate that long-lasting verapamil-resistant drug efflux mechanisms are activated in brain endothelial cells after irradiation. The results might explain the poor efficacy of chemotherapy following radiotherapy and contribute to consideration of new treatment strategies in the management of malignant glioma.

Inhibition of growth of MDA-MB-468 estrogen-independent human breast carcinoma by bombesin/gastrin-releasing peptide antagonists RC-3095 and RC-3940-II

BACKGROUND

The growth of breast carcinoma is promoted by autocrine growth factors such as the bombesin (BN)-like peptides and epidermal growth factor (EGF). The stimulatory action of BN-like peptides can be blocked by the use of BN/gastrin-releasing peptide (GRP) antagonists.

METHODS

The authors investigated the effects of synthetic BN/GRP antagonists RC-3095 and RC-3940-II on tumor growth and the expression of mRNA for EGF receptors and three BN receptor subtypes in MDA-MB-468 human breast carcinoma. Athymic nude mice with xenografts of MDA-MB-468 human breast carcinoma were injected subcutaneously for 6 weeks with RC-3940-II at doses of 20 or 40 microg/day. In another study, the effects of RC-3940-II and RC-3095 were compared.

RESULTS

RC-3940-II caused a significant and dose-dependent growth inhibition of MDA-MB-468 tumors in nude mice; therapy with either dose of RC-3940-II significantly (P<0.01) reduced the mean final tumor volume and weight compared with controls. RC-3940-II induced a persistent regression of > 50% of all tumors. One of 3 tumors treated with 20 microg of RC-3940-II and 3 of 5 tumors treated with 40 microg were found to have regressed completely by the end of the study. When RC-3940-II and RC-3095 were compared at the dose of 20 microg/day, both powerfully suppressed growth of MDA-MB-468 tumors, with RC-3940-II causing a complete regression of 2 tumors and RC-3095 a complete regression of 1 tumor. Receptor analyses of untreated MDA-MB-468 tumors revealed an overexpression of EGF receptors and two classes of binding sites for BN/GRP. mRNAs for receptors of GRP, neuromedin B, and BN receptor subtype-3 were detected by reverse transcriptase-polymerase chain reaction.

CONCLUSIONS

A virtual arrest of growth or regression of MDA-MB-468 human breast carcinoma after therapy with RC-3940-II and RC-3095 indicates that these BN/GRP antagonists could provide a new treatment modality for breast tumors expressing BN and EGF receptors.

Parallel increase in substance P and VIP in rat duodenum in response to irradiation

Irradiation was administered to the upper abdomen of rats, whereupon the duodenum was examined. Numerous vasoactive intestinal peptide (VIP)- and substance P (SP)-like immunoreactive nerve fibers were seen in the damaged mucosa, often in close association to each other. The intensity of the SP- and VIP-like immunoreaction was increased in several of the tissue compartments and, as measured with radioimmunoassay, the contents of SP- and VIP-like materials were increased after 30 Gray. The results show that SP and VIP levels increase after irradiation and suggest that SP and VIP are involved in interactive reactions in the reorganization and inflammatory processes in the gut after abdominal irradiation.