Preclinical studies on the broad-spectrum neuropeptide growth factor antagonist G

Metastatic Breast Cancer, Organotropism and Therapeutics: A Review

The final stage of breast cancer involves spreading breast cancer cells to the vital organs like the brain, liver lungs and bones in the process called metastasis. Once the target organ is overtaken by the metastatic breast cancer cells, its usual function is compromised causing organ dysfunction and death. Despite the significant research on breast cancer metastasis, it's still the main culprit of breast cancer-related deaths. Exploring the complex molecular pathways associated with the initiation and progression of breast cancer metastasis could lead to the discovery of more effective ways of treating the devastating phenomenon. The present review article highlights the recent advances to understand the complexity associated with breast cancer metastases, organotropism and therapeutic advances.

Fungal Aflatoxins Reduce Respiratory Mucosal Ciliary Function

Aflatoxins are mycotoxins secreted by Aspergillus flavus, which can colonize the respiratory tract and cause fungal rhinosinusitis or bronchopulmonary aspergillosis. A. flavus is the second leading cause of invasive aspergillosis worldwide. Because many respiratory pathogens secrete toxins to impair mucociliary immunity, we examined the effects of acute exposure to aflatoxins on airway cell physiology. Using air-liquid interface cultures of primary human sinonasal and bronchial cells, we imaged ciliary beat frequency (CBF), intracellular calcium, and nitric oxide (NO). Exposure to aflatoxins (0.1 to 10 μM; 5 to 10 minutes) reduced baseline (~6-12%) and agonist-stimulated CBF. Conditioned media (CM) from A. fumigatus, A. niger, and A. flavus cultures also reduced CBF by ~10% after 60 min exposure, but effects were blocked by an anti-aflatoxin antibody only with A. flavus CM. CBF reduction required protein kinase C but was not associated with changes in calcium or NO. However, AFB2 reduced NO production by ~50% during stimulation of the ciliary-localized T2R38 receptor. Using a fluorescent reporter construct expressed in A549 cells, we directly observed activation of PKC activity by AFB2. Aflatoxins secreted by respiratory A. flavus may impair motile and chemosensory functions of airway cilia, contributing to pathogenesis of fungal airway diseases.

G protein-coupled receptor systems and their lipid environment in health disorders during aging

Cells, tissues and organs undergo phenotypic changes and deteriorate as they age. Cell growth arrest and hyporesponsiveness to extrinsic stimuli are all hallmarks of senescent cells. Most such external stimuli received by a cell are processed by two different cell membrane systems: receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs). GPCRs form the largest gene family in the human genome and they are involved in most relevant physiological functions. Given the changes observed in the expression and activity of GPCRs during aging, it is possible that these receptors are directly involved in aging and certain age-related pathologies. On the other hand, both GPCRs and G proteins are associated with the plasma membrane and since lipid-protein interactions regulate their activity, they can both be considered to be sensitive to the lipid environment. Changes in membrane lipid composition and structure have been described in aged cells and furthermore, these membrane changes have been associated with alterations in GPCR mediated signaling in some of the main health disorders in elderly subjects. Although senescence could be considered a physiologic process, not all aging humans develop the same health disorders. Here, we review the involvement of GPCRs and their lipid environment in the development of the major human pathologies associated with aging such as cancer, neurodegenerative disorders and cardiovascular pathologies.

Targeting Stealth liposomes in a murine model of human small cell lung cancer

Tumor accumulation and therapeutic activity of Stealth liposomes loaded with doxorubicin (DXR) were examined in Balb/c nude mice xenografts inoculated subcutaneously with the human small cell lung cancer (SCLC) cell line, H69. Mice were treated with non-targeted liposomes (SL) or liposomes targeted with antagonist G coupled to the liposome surface (SLG). SLG showed 30-44-fold higher binding to H69 cells harvested from H69 xenografts than SL. At 48 and 72 h post injection, tumor accumulation of [(125)I]tyraminylinulin-containing liposomes was shown to be dependent on liposome size but independent of the presence of the targeting ligand. Maximum tumor uptake of either SLG or SL ranged from 2 to 4% of injected dose/g of tissue. In therapeutic studies, mice received three weekly injections of 3 or 6 mg free DXR/kg or 3 or 10 mg liposomal DXR/kg at initial tumor volumes of either 7 or 33 mm(3). The therapeutic efficacy of DXR-containing SL or SLG was significantly improved over free DXR, but SLG did not improve anti-tumor efficacy relative to SL. Stealth liposomes containing DXR have potential as a therapy against human SCLC tumors.

A growth factor antagonist as a targeting agent for sterically stabilized liposomes in human small cell lung cancer

The ability of a growth factor antagonist, [D-Arg(6),D-Trp(7,9)-N(me)Phe(8)]-substance P(6-11), named antagonist G, to selectively target polyethylene glycol-grafted liposomes (known as sterically stabilized liposomes) to a human classical small cell lung cancer (SCLC) cell line, H69, was examined. Our results showed that radiolabeled antagonist G-targeted sterically stabilized liposomes (SLG) bound to H69 cells with higher avidity than free antagonist G and were internalized (reaching a maximum of 13000 SLG/cell), mainly through a receptor-mediated process, likely involving clathrin-coated pits. This interaction was confirmed by confocal microscopy to be peptide- and cell-specific. Moreover, it was shown that SLG significantly improved the nuclear delivery of encapsulated doxorubicin to the target cells, increasing the cytotoxic activity of the drug over non-targeted liposomes. In mice, [(125)I]tyraminylinulin-containing SLG were long circulating, with a half-life of 13 h. Use of peptides like antagonist G to promote binding and internalization of sterically stabilized liposomes, with their accompanying drug loads, i.e., anticancer drugs, genes or antisense oligonucleotides, into target cells has the potential to improve therapy of SCLC.

Treatment of extensive stage small cell lung cancer

Over the past twenty years combination chemotherapy has continued to produce small survival gains for patients with SCLC. We enter the next century enthusiastic about the array of new chemotherapeutic agents to evaluate and fascinated by the biological agents with the hope of achieving dramatic improvements in survival for our patients with SCLC.

Therapeutic advances in small cell lung cancer

Small cell lung cancer (SCLC) is characterised by neuroendocrine differentiation, early metastatic potential and initial responsiveness to cytotoxic therapy. Unfortunately, despite recent therapeutic advances, most patients relapse and the overall five-year survival rate is only 5%. Standard treatment of SCLC consists of platinum-based combination chemotherapy, with thoracic irradiation added for patients with limited-stage disease. Several newer chemotherapeutic drugs have recently been shown to have significant activity in patients with untreated or relapsed SCLC. These agents include: the topoisomerase I inhibitors, topotecan and irinotecan; the taxanes, paclitaxel and docetaxel; the pyrimidine analogue, gemcitabine; and the vinca alkaloid, vinorelbine. Recent advances in our understanding of the molecular events involved in the pathogenesis and progression of SCLC have led to the identification of a variety of potential targets for novel therapeutic interventions. Strategies aimed at inhibiting the myriad of growth factor pathways that control the proliferation of SCLC cells, include: broad spectrum neuropeptide antagonists (e.g., substance P analogues); growth factor/receptor-specific inhibitors (e.g., anti-GRP monoclonal antibodies, bradykinin antagonist dimers); and a variety of selective protein kinase inhibitors. The importance of cell death pathways in carcinogenesis and treatment-resistance has led to several novel strategies targeting apoptotic mediators, such as bcl-2, that are frequently dysregulated in SCLC (e.g., bcl-2 antisense). Our current challenges are to further refine these promising therapeutic strategies, efficiently evaluate their activity in the clinical setting and integrate them into more effective treatment regimens to improve the overall prognosis of patients with SCLC.

Increased expression of preprotachykinin-I and neurokinin receptors in human breast cancer cells: implications for bone marrow metastasis

Neuropeptides are implicated in many tumors, breast cancer (BC) included. Preprotachykinin-I (PPT-I) encodes multiple neuropeptides with pleiotropic functions such as neurotransmission, immune/hematopoietic modulation, angiogenesis, and mitogenesis. PPT-I is constitutively expressed in some tumors. In this study, we investigated a role for PPT-I and its receptors, neurokinin-1 (NK-1) and NK-2, in BC by using quantitative reverse transcription-PCR, ELISA, and in situ hybridization. Compared with normal mammary epithelial cells (n = 2) and benign breast biopsies (n = 21), BC cell lines (n = 7) and malignant breast biopsies (n = 25) showed increased expression of PPT-I and NK-1. NK-2 levels were high in normal and malignant cells. Specific NK-1 and NK-2 antagonists inhibited BC cell proliferation, suggesting autocrine and/or intercrine stimulation of BC cells by PPT-I peptides. NK-2 showed no effect on the proliferation of normal cells but mediated the proliferation of BC cells. Cytosolic extracts from malignant BC cells enhanced PPT-I translation whereas extracts from normal mammary epithelial cells caused no change. These enhancing effects may be protein-specific because a similar increase was observed for IL-6 translation and no effect was observed for IL-1alpha and stem cell factor. The data suggest that PPT-I peptides and their receptors may be important in BC development. Considering that PPT-I peptides are hematopoietic modulators, these results could be extended to understand early integration of BC cells in the bone marrow, a preferred site of metastasis. Molecular signaling transduced by PPT-I peptides and the mechanism that enhances translation of PPT-I mRNA could lead to innovative strategies for BC treatments and metastasis.

Synthesis of peptide and pseudopeptide amides inhibiting the proliferation of small cell and epithelial types of lung carcinoma cells

Small cell lung cancer (SCLC) cell lines produce and secrete various peptide hormones, e.g. bombesin (BN)/gastrin releasing peptide (GRP) like peptides that are proposed to function as their autocrine growth factors. To inhibit the proliferative effect of these hormones we have synthesized short chain BN[7-14]-analogues replacing the C-terminal peptide bond by a methylene-amino (-CH2NH-) unit and introducing D-Phe or D-Ser into position 12. As several substance P (SP) analogues were found to inhibit the growth of SCLC cells, some short chain SP-analogues have been synthesized. (Pseudo)octapeptides were synthesized in solution, by fragment condensation using the DCC/HOPfp method. Fragments and SP-analogues were synthesized stepwise using pentafluorophenyl esters. The resistance to hydrolysis of the reduced peptide bond made permitted exact quantification of the Leupsi(CH2NH)Leu pseudopeptide in hydrolysates. The binding ability of both types of peptides to BN-receptors on Swiss 3T3 mouse fibroblast cells and their antiproliferative effect on NCI-H69 human SCLC cell line have been tested and compared with a short chain SP-antagonist pHOPA-D-Trp-Phe-D-Trp-Leu-Leu-NH2 (R) previously described as a potent inhibitor of SCLC proliferation. While BN-analogues showed weak activity in inhibition of proliferation of SCLC cells, SP-analogues 6: D-MePhe-D-Trp-Phe-D-Trp-Leu(psi)(CH2NH)-Leu-NH2 and 7: D-MePhe-DTrp-Phe-D-Trp-Leu-MPA, in spite of greatly diminished affinity towards the BN-receptor, inhibited SCLC proliferation more effectively than R (6: IC50 = 2 microM, 7: IC50 = 5 microM and R: IC50 = 10 microM). Moreover, 6 inhibited the respiratory activity of SK-MES 1 epithelial type of lung carcinoma cells in proliferating but not in the quiescent state, suggesting that the antiproliferative effect of these compounds is not due to simple cytotoxicity. These short chain analogues of SP might be promising candidates as therapeutic agents in the treatment of SCLC.

Induction of apoptosis by a short-chain neuropeptide analog in small cell lung cancer

Small cell lung cancer (SCLC) cells express a variety of neuropeptides which act as autocrine growth factors. Although several neuropeptide analogs have been reported to antagonize SCLC proliferation, the development of these compounds has been limited by their low potency and the cytostatic nature of their effects. In the present study we evaluated the cytotoxic activity of four short-chain substance P analogs (NY3460, NY3238[-pHOPA], NY3238[Phe1], NY3238[Lys5]) against a panel of five SCLC cell lines. NY3460 was the most potent compound in all five SCLC cell lines (IC50 = 2.8-3.7 microM) as assessed by a MTT growth inhibitory assay. NY3238[Phe1] was also relatively active in all cell lines (IC50 = 3.5-11.2 microM), while NY3238[Lys5] and NY3238[-pHOPA] were substantially less active. NY3460 was the only agent to induce an increase in the percentage of cells with subdiploid DNA content suggestive of apoptosis by flow cytometric DNA content analysis. The induction of apoptosis was confirmed by fluorescent microscopy in NCI-H69, NCI-H82, NCI-H446, and NCI-H510 cells after exposure to 5.0 microM NY3460 for 48 h. These findings suggest that NY3460 is a relatively potent cytotoxic inhibitor of SCLC growth, and that short-chain neuropeptide analogs deserve further evaluation as anti-SCLC agents.