Docetaxel in combination with octreotide shows synergistic apoptotic effect by increasing SSTR2 and SSTR5 expression levels in prostate and breast cancer cell lines

Somatostatin and Somatostatin Receptors in Tumour Biology

Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.

Transcriptomic analysis of adult zebrafish heart and brain in response to 2, 6-dichloro-1, 4-benzoquinone exposure

Halobenzoquinones (HBQs) are emerging and widespread disinfection byproducts (DBPs), but their toxicological mechanisms to aquatic organisms remain elusive. Herein, we evaluated oxidative stress, cardiac toxicity, and cerebral toxicity after 2, 6-dichloro-1, 4-benzoquinone (2,6-DCBQ) exposure in zebrafish. Adult zebrafish were respectively exposed to 0.25, 0.5, and 1 μM 2,6-DCBQ for 96 h. The mortality rate of 2,6-DCBQ (1 μM) was 10%, while the LC50 value was 1.532 μM. Besides, 2,6-DCBQ exposure caused irregularity and elimination of myocardial fiber in the heart, and the pyknosis of nuclears and the agglutination of chromatin in the brain. We measured the 2,6-DCBQ-induced oxidative stresses in the heart and brain. Additionally, the glutathione (GSH) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, and total antioxidant capacity (T-AOC) were significantly inhibited. To better understand the potential toxicity of 2,6-DCBQ, transcriptomic analysis was performed in the control and 1 μM group after 96 h exposure. As a result, 545 and 1228 differentially expressed genes (DEGs) were detected in the heart and brain, respectively. GO analysis revealed that these DEGs were primarily enriched in blood vessel development, vasculature development, and oxidoreductase activity in the heart; response to stimulus, nervous system development, and oxidoreductase activity in the brain. KEGG enrichment analysis indicated that the DEGs were mainly enriched in VEGF signaling pathway and vascular smooth muscle contraction pathway in the heart; neuroactive ligand-receptor interaction, and NOD-like receptor signaling pathway in the brain. These findings exposed the underlying toxicity mechanism of 2,6-DCBQ exposure on zebrafish cardiovascular and brain systems.

Novel fusion protein NGR-sIL-24 for targetedly suppressing cancer cell growth via apoptosis

Pro-apoptotic peptides have attracted much attention as promising anticancer agents due to their high activity. However, poor cellular uptake of the peptides is often associated with limited therapeutic application. Cell-penetrating homing peptides (CPHPs) were found to increase cell internalization as well as anticancer efficacy of the peptide conjugates. In this study, we developed a novel recombinant fusion protein composed of sIL-24 peptide as a pro-apoptotic moiety and asparagine-glycine-arginine (NGR) motif as a CD13-targeting CPHP component. In silico analysis demonstrated that flexible GGGGS linker provided the best structure and stability for our designed fusion protein. Cell adhesion experiments showed a significant binding affinity toward high CD13-expressing cells (U937 and A549) for NGR-sIL-24. Moreover, confocal microscopy revealed that NGR strongly facilitated the binding and cellular uptake of sIL-24 in U937 and A549 cancer cells. NGR-sIL-24 treatment markedly inhibited the growth of U937 and A549 cancer cells in a dose and time-dependent manner, without affecting the normal cell line MRC-5. Flow cytometric analysis and Hoechst 33342 staining exhibited potent apoptosis induction in U937 and A549 cells treated with NGR-sIL-24. Further mechanism elucidation uncovered that apoptotic death promoted by NGR-sIL-24 was attributed to upregulation of BiP/GRP78, Bax/Bcl-2, GADD34, cytochrome c release, and cleavage of caspase-3, suggesting NGR-sIL-24 penetration into cancerous cells and subsequent apoptosis induction, mainly through endoplasmic reticulum (ER) stress-dependent and mitochondria-dependent signaling pathways. Our results indicate that the designed recombinant fusion protein NGR-sIL-24 may serve as a potential targeted therapy agent for cancers with high expression of CD13.

Next-generation paclitaxel-nanoparticle formulation for pancreatic cancer treatment

Pancreatic cancer (PanCa) is a major cause of cancer-related death due to limited therapeutic options. As pancreatic tumors are highly desmoplastic, they prevent appropriate uptake of therapeutic payloads. Thus, our objective is to develop a next-generation nanoparticle system for treating PanCa. We generated a multi-layered Pluronic F127 and polyvinyl alcohol stabilized and poly-L-lysine coated paclitaxel loaded poly(lactic-co-glycolic acid) nanoparticle formulation (PPNPs). This formulation exhibited optimal size (~160 nm) and negative Zeta potential (-6.02 mV), efficient lipid raft mediated internalization, pronounced inhibition in growth and metastasis in vitro, and in chemo-naïve and chemo-exposed orthotopic xenograft mouse models. Additionally, PPNPs altered nanomechanical properties of PanCa cells as suggested by the increased elastic modulus in nanoindentation analyses. Immunohistochemistry of orthotopic tumors demonstrated decreased expression of tumorigenic and metastasis associated proteins (ki67, vimentin and slug) in PPNPs treated mice. These results suggest that PPNPs represent a viable and robust platform for (PanCa).

Pulmonary Carcinoid Surface Receptor Modulation Using Histone Deacetylase Inhibitors

Pulmonary carcinoids are a type of neuroendocrine tumor (NET) accounting for 1-2% of lung cancer cases. Currently, Positron Emission Tomography (PET)/CT based on the radiolabeled sugar analogue [18F]-FDG is used to diagnose and stage pulmonary carcinoids, but is suboptimal due to low metabolic activity in these tumors. A new technique for pulmonary carcinoid imaging, using PET/CT with radiolabeled somatostatin analogs that specifically target somatostatin receptor subtype 2 (SSTR2), is becoming more standard, as many tumors overexpress SSTR2. However, pulmonary carcinoid patients with diminished SSTR2 expression are not eligible for this imaging or any type of SSTR2-specific treatment. We have found that histone deacetylase (HDAC) inhibitors can upregulate the expression of SSTR2 in pulmonary carcinoid cell lines. In this study, we used a non-cytotoxic dose of HDAC inhibitors to induce pulmonary carcinoid SSTR2 expression in which we confirmed in vitro and in vivo. A non-cytotoxic dose of the HDAC inhibitors: thailandepsin A (TDP-A), romidepsin (FK228), suberoylanilide hydroxamic acid (SAHA), AB3, and valproic acid (VPA) were administered to promote SSTR2 expression in pulmonary carcinoid cell lines and xenografts. This SSTR2 upregulation technique using HDAC inhibitors could enhance radiolabeled somatostatin analog-based imaging and the development of potential targeted treatments for pulmonary carcinoid patients with marginal or diminished SSTR2 expression.

In vitro and in vivo effects of a recombinant anti-PSMA immunotoxin in combination with docetaxel against prostate cancer

Docetaxel (DOC) is used for the first-line treatment of castration resistant prostate cancer (CPRC). However, the therapeutic effects are limited, only about one half of patients respond to the therapy and severe side effects possibly lead to discontinuation of treatment. Therefore, actual research is focused on the development of new DOC-based combination treatments.

In this study we investigated the antitumor effects of a recombinant immunotoxin targeting the prostate specific membrane antigen (PSMA) in combination with DOC in vitro and in vivo. The immunotoxin consists of an anti-PSMA single chain antibody fragment (scFv) as binding and a truncated form of Pseudomonas aeruginosa Exotoxin A (PE40) as toxin domain. The immunotoxin induced apoptosis and specifically reduced the viability of androgen-dependent LNCaP and androgen-independent C4-2 prostate cancer cells. A synergistic cytotoxic activity was observed in combination with DOC with IC₅₀ values in the low picomolar or even femtomolar range. Moreover, combination treatment resulted in an enhanced antitumor activity in a C4-2 SCID mouse xenograft model. This highlights the immunotoxin as a promising therapeutic agent for a future DOC-based combination therapy of CPRC.

Octreotide Attenuates Acute Kidney Injury after Hepatic Ischemia and Reperfusion by Enhancing Autophagy

Octreotide exerts a protective effect in hepatic ischemia-reperfusion (HIR) injury. However, whether octreotide preconditioning could also reduce acute kidney injury (AKI) after HIR is unknown. This study was designed to investigate the role of octreotide in AKI after HIR. Male Sprague-Dawley rats were pretreated with octreotide or octreotide combined with 3-methyladenine (autophagy inhibitor, 3MA). Plasma creatinine, inflammation markers (e.g., TNF-α and IL-6 etc.), apoptosis, autophagy and phosphorylation of protein kinase B/mammalian target of rapamycin/p70 ribosomal S6 kinase (Akt/mTOR/p70S6K) in the kidney were measured after 60 minutes of liver ischemia and 24 hours of reperfusion for each rat. Octreotide pretreatment significantly preserved renal function and reduced the severity of renal injury. Moreover, octreotide alleviated inflammation and apoptosis in the kidney after HIR. Additionally, octreotide induced autophagy and autophagy inhibition with 3MA markedly reversed the renoprotective, anti-inflammatory and anti-apoptotic effects of octreotide after HIR. Finally, octreotide abrogated the activation of phosphorylation of Akt, mTOR and p70S6K in the kidney after HIR. Our results indicate that octreotide reduced renal injury after HIR due to its induction of autophagy. The enhancement of autophagy may be potentially linked to the octreotide mediated Akt/mTOR/p70S6K pathway deactivation and reduction of kidney inflammation and apoptosis after HIR.

Somatostatin receptor targeted liposomes with Diacerein inhibit IL-6 for breast cancer therapy

Selective targeting to the tumor niche remains a major challenge in successful cancer therapy. Somatostatin receptor 2 (SSTR2) is overexpressed in breast cancer cells thus making this receptor an attractive target for selective guidance of ligand-conjugated drug liposomes to the tumor site. In this study, a synthetic somatostatin analogue (SST) was used as SSTR2 targeting agent and Diacerein was employed as therapeutic molecule. Diacerein loaded liposomes (DNL) were prepared and they were further decorated with the synthetic and stable analogue of somatostatin (SST-DNL). Fabricated liposomes were nano-size in range and biocompatible. SST-DNL displayed significantly better anti-tumor efficacy as compared to free Diacerein (DN) and DNL in breast cancer models. Enhanced apoptosis in breast cancer cells was detected in SST-DNL treated groups as monitored by cell cycle analysis and changes in expression level of apoptotic/anti-apoptotic proteins Bcl-2, Bax, cleaved Caspase 3 and PARP. SST-DNL more effectively inhibited the oncogenic IL-6/IL-6R/STAT3/MAPK/Akt signalling pathways as compared to DN or DNL in cancer cells. In addition, SST-DNL effectively suppressed angiogenesis and cancer cell invasion. In vivo tumor growth in a MDA-MB-231 mouse xenograft model was significantly suppressed following SST-DNL treatment. In xenograft model, immunohistochemistry of Ki-67 and CD-31 indicated that SST-DNL improved the anti-proliferative and anti-angiogenic impacts of Diacerein. In vivo pharmacokinetic studies in rats showed enhanced circulation time in the DNL or SST-DNL treated groups as compared to free DN. Considering all of these findings, we conclude that SST-DNL provides a novel strategy with better efficacy for breast cancer therapy.

Clinical studies in humans targeting the various components of the IGF system show lack of efficacy in the treatment of cancer

The insulin-like growth factors (IGFs) system regulates cell growth, differentiation and energy metabolism and plays crucial role in the regulation of key aspects of tumor biology, such as cancer cell growth, survival, transformation and invasion. The current focus for cancer therapeutic approaches have shifted from the conventional treatments towards the targeted therapies and the IGF system has gained a great interest as anti-cancer therapy. The proliferative, anti-apoptotic and transformation effects of IGFs are mainly triggered by the ligation of the type I IGF receptor (IGF-IR). Thus, aiming at developing novel and effective cancer therapies, different strategies have been employed to target IGF system in human malignancies, including but not limited to ligand or receptor neutralizing antibodies and IGF-IR signaling inhibitors. In this review, we have focused on the clinical studies that have been conducted targeting the various components of the IGF system for the treatment of different types of cancer, providing a description and the challenges of each targeting strategy and the degree of success.