Highly cytotoxic maytansine derivatives are widely used in targeted tumor delivery. Structure-activity studies published earlier suggested the C9 carbinol to be a key element necessary to retain the potency. However, in 1984 a patent was published by Takeda in which the synthesis of 9-thioansamitocyn (AP3SH) was described and its activity in xenograft models was shown. In this article we summarize the results of an extended study of the anti-tumor properties of AP3SH. Like other maytansinoids, it induces apoptosis and arrests the cell cycle in the G2/M phase. It is metabolized in liver microsomes predominately by C3A4 isoform and doesn't inhibit any CYP isoforms except CYP3A4 (midazolam, IC50 7.84 μM). No hERG inhibition, CYP induction or mutagenicity in Ames tests were observed. AP3SH demonstrates high antiproliferative activity against 25 tumor cell lines and tumor growth inhibition in U937 xenograft model. Application of AP3SH as a cytotoxic payload in drug delivery system was demonstrated by us earlier.

Multiple drug-targeting strategies have been applied to drug development in order to reduce the toxic side effects of the traditional chemotherapy while enhancing its anti-tumor efficacy. Various peptides, proteins and antibodies are usually used to conjugate cytotoxic agents via acting as drug delivery vehicles. In our previous studies, we identified that peptides displayed their efficacious functions to deliver small molecules or oligo DNA to the target sites through ligand-receptor interactions and quick internalization. In our present study, we attempt to synthesize serial drug conjugates via coupling these compounds to peptide or protein vehicles. Tye1001, one of these conjugates, displayed similar potent anti-proliferation activities in lymphoma cells and many other cancer cells compared to the small molecule itself. In particular, this conjugate significantly enhanced its potent anti-tumor efficacy in xenografts. Meanwhile, this conjugate has much less toxic side effects. In our in vivo assays, the similar results were also observed in multiple other tumors such as gastric cancer and leukemia. Our findings provide a more potential druggable opportunity in the clinical applications of cancer patients and the treatment of different types of cancers. Citation Format: Lichun Sun, Mengli Yang, Haihua Xiao, Yuan Tian, Natalya Vasilevich, Joseph Fuselier, David Coy. The targeting drug conjugate Tye1001 displayed its potent anti-tumor efficacy in lymphoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4957.

The human serum albumin (HSA) is produced in the hepatocytes of human livers and is the most abundant protein in blood. HSA consists of one N-terminus, one C-terminus and three homologous domains, each of which has two helical subdomains. HSA enjoys advantages such as long half-life, repeated recycling, and specific accumulation. HSA has several binding pockets where various ligands such as fatty acids, ions can bind to, providing drugs the option for non-covalent binding sites. Meanwhile, two terminal ends of albumin and certain amino acid residues provide more choices for drug targeting. The free amino acid cysteine at the position 34 (Cys34) is located on the surface of albumin and provides a unique thiol group for drugs of interest to be covalently coupled with. The two terminal ends of albumin can be fused with peptides or proteins of interest by molecular recombinant technology. Importantly, HSA can retain its binding affinity in albumin-FcRn interactions after being covalently or non-covalently coupled with various drugs. HSA can also extend the half-life of drugs, reduce renal clearance of drugs and help accumulate drugs in specific tumor tissues. HSA provides a promising opportunity for delivering established medications in a new way.

Nowadays, the bacterial drug resistance leads to serious healthy problem worldwide due to the long-term use and the abuse of traditional antibiotics result in drug resistance of bacteria. Finding a new antibiotic is becoming more and more difficult. Antimicrobial peptides (AMPs) are the host defense peptides with most of them being the cationic (positively charged) and amphiphilic (hydrophilic and hydrophobic) α-helical peptide molecules. The membrane permeability is mostly recognized as the well-accepted mechanism to describe the action of cationic AMPs. These cationic AMPs can bind and interact with the negatively charged bacterial cell membranes, leading to the change of the electrochemical potential on bacterial cell membranes, inducing cell membrane damage and the permeation of larger molecules such as proteins, destroying cell morphology and membranes and eventually resulting in cell death. These AMPs have been demonstrated to have their own advantages over the traditional antibiotics with a broad-spectrum of antimicrobial activities including anti-bacteria, anti-fungi, anti-viruses, and anti-cancers, and even overcome bacterial drug-resistance. The natural AMPs exist in a variety of organisms and are not stable with a short half-life, more or less toxic side effects, and particularly may have severe hemolytic activity. To open the clinical applications, it is necessary and important to develop the synthetic and long-lasting AMP analogs that overcome the disadvantages of their natural peptides and the potential problems for the drug candidates.

Nowadays, most of current digital data are mainly stored on magnetic and optical media. At the explosive era of digital data, the digital data are generated every day and increased at an exponential rate. These traditional media cannot meet the urgent requirement of big digital data storage. With such advantages as high density, high replication efficiency, long-term durability and long-term stability, deoxyribonucleic acid (DNA) is expected as a novel and potential data storage medium. For the new DNA data storage, the files or any data readable will be converted to binary and then encoded to DNA sequences consisting of Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). The data-carrying DNA sequences will be synthesized and stored until data retrieval one day. Once data retrieval, the unique data-carrying DNA fragments will be amplified, sequenced and analyzed. The DNA-based data information will then be decoded into binary and eventually converted to the information readable. Currently, the application of DNA data storage is limited due to such disadvantages as high cost, time-consuming, lack of random access ability. We still need to face serial tough challenges. However, the seen advances in DNA sequencing technology positively shine the future of DNA digital data storage.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a naturally occurring cationic peptide with potent immunosuppressant and cytoprotective activities. We now show that full length PACAP38 and to a lesser extent, the truncated form PACAP27, and the closely related vasoactive intestinal peptide (VIP) and secretin had antimicrobial activity against the Gram-negative bacteria Escherichia coli in the radial diffusion assay. PACAP38 was more potent than either the bovine neutrophil antimicrobial peptide indolicidin or the synthetic antimicrobial peptide ARVA against E. coli. PACAP38 also had activity against the Gram-positive bacteria Staphylococcus aureus in the same assay with comparable potency to indolicidin and ARVA. In the more stringent broth dilution assay, PACAP38 had moderate sterilizing activity against E. coli, and potent sterilizing activity against the Gram-negative bacteria Pseudomonas aeruginosa. PACAP27, VIP and secretin were much less active than PACAP38 in this assay. PACAP38 also had some activity against the Gram-positive bacteria Bacillus cereus in the broth dilution assay. Many exopeptidase-resistant analogs of PACAP38, including both receptor agonists and antagonists, had antimicrobial activities equal to, or better than PACAP38, in both assays. PACAP38 made the membranes of E. coli permeable to SYTOX Green, suggesting a classical membrane lytic mechanism. These data suggest that analogs of PACPAP38 with a wide range of useful biological activities can be made by judicious substitutions in the sequence.

Small cell lung cancer (SCLC) is a malignant human cancer and patients have very limited benefit from traditional anticancer treatments, with a poor five-year survival rate being 10% less. In present study, we observed that Notch signalling activation induced SCLC cell growth suppression via overexpressing Notch active fragments (ICN1, ICN2, ICN3 and ICN4), implying its tumor suppressive role. The histone deacetylase (HDAC) inhibitors also displayed their suppressive effects. Valproic acid (VPA) as a HDAC inhibitor was found to suppress SCLC cell growth and cell cycle arrest at phase G1, and observed to decrease HDAC4 and increase acetylation of histone H4 (AcH4) while activating Notch signalling with an increase of Notch1, Notch target gene HES1 and p21. Meanwhile, we also observed that VPA greatly stimulated the expression of somatostatin receptor type II (SSTR2) that is usually overexpressed in many cancer cells and is used as a target for anticancer drug development, providing a combination therapy with VPA and the SSTR2-targeting cytotoxins. Thus, VPA was investigated in combination with SSTR2-targeted cytotoxins captothecine-somatostatin conjugate (CPT-SST) and colchicine-somatostatin conjugate (COL-SST). Our assays showed that these combination treatments strongly led to a greater suppression as compared to each alone. In conclusion, we found that VPA suppressed SCLC cell growth and increased the expression of SSTR2. These may provide a novel clinical opportunity for enhanced anticancer therapy using the combination strategy of Notch signalling regulator and SSTR2-targeting cytotoxins in SCLC treatments.

Mitoxantrone (MXT) is an androstenedione that is used to treat cancers and progressive forms of multiple sclerosis; however, its use is limited by its cardiotoxicity. Pituitary adenylate cyclase activating polypeptide (PACAP) is a member of the secretin/growth hormone-releasing hormone/vasoactive intestinal peptide family and has many functions, including cytoprotection and immunosuppression. We tested the hypothesis that PACAP can protect against MXT-induced cardiotoxicity in mice. Female BALB/c mice were treated once weekly for 4 weeks with saline (n=14) or MXT (3mg/kg, i.p.; n=14). Half of the mice in each group received PACAP (10μg, i.p.) 1h before and 24 and 48h after MXT, while the remaining mice received injections of saline on the same schedule. Echocardiography was used to assess cardiac structure and function. In mice treated with MXT and saline, body weight was significantly reduced after the third dose of MXT. PACAP significantly attenuated the reduction in body weight; however, the weights did not return to control level. Compared to controls, MXT-treated mice had significantly increased left ventricular (LV) diameter and LV volume and decreased LV posterior wall thickness. Fractional shortening (FS) and ejection fraction (EF) were also significantly decreased. Treatment with PACAP prevented MXT-induced LV dilation and significantly attenuated the reductions in FS and EF, although FS and EF did not return to control level. PACAP38 did not prevent MXT-induced decreases in LV posterior wall thickness. MXT dose-dependently decreased the viability of cultured U937 (human leukemia) cells; PACAP did not protect cultured U937 cells from MXT-mediated cell death. In conclusion, PACAP can attenuate MXT-mediated LV dilation and dysfunction in mice.

Multiple Gαi protein-coupled somatostatin receptors (SSTRs) are expressed in human kidney and liver tissues. Also, aberrant cAMP signaling has been shown to play a critical role in cysto-genesis and enlargement of the human kidney and liver. Thus, somatostatin (SST) analogs become potential and promising alternatives in treating human polycystic kidney disease (PKD) and polycystic liver disease (PLD) via interacting with Gαi protein-coupled SSTRs and further blocking cAMP production. Lanreotide is a synthetic, long-acting SST analog with high binding affinity to SSTR2, and has been clinically approved for the treatment of acromegaly due to excessive growth hormone. Recently, this SST analog has been applied in the treatment of PKD and PLD, and has shown an effective reduction of liver and kidney volume compared to placebo. This review will discuss the discovery of this peptide and its clinical applications in the treatment of PKD/PLD patients.

Aims/hypothesis Regular exercise is at the cornerstone of care in type 1 diabetes. However, relative hyperinsulinaemia and a blunted glucagon response to exercise promote hypoglycaemia. Recently, a selective antagonist of somatostatin receptor 2, PRL-2903, was shown to improve glucagon counterregulation to hypoglycaemia in resting streptozotocin-induced diabetic rats. The aim of this study was to test the efficacy of PRL-2903 in enhancing glucagon counterregulation during repeated hyperinsulinaemic exercise.Methods Diabetic rats performed daily exercise for 1 week and were then exposed to saline (154 mmol/l NaCl) or PRL-2903, 10 mg/kg, before hyperinsulinaemic exercise on two separate occasions spaced 1 day apart. In the following week, animals crossed over to the alternate treatment for a third hyperinsulinaemic exercise protocol.Results Liver glycogen content was lower in diabetic rats compared with control rats, despite daily insulin therapy (p < 0.05). Glucagon levels failed to increase during exercise with saline but increased three-to-six fold with PRL-2903 (all p < 0.05). Glucose concentrations tended to be higher during exercise and early recovery with PRL-2903 on both days of treatment; this difference did not achieve statistical significance (p > 0.05).Conclusions/interpretation PRL-2903 improves glucagon counterregulation during exercise. However, liver glycogen stores or other factors limit the prevention of exercise-induced hypoglycaemia in rats with streptozotocin-induced diabetes.

Somatostatin (SST) is a cyclic hormone-release inhibitory peptide that has high binding affinity to all of its five SST receptors (SSTRs). SST negatively regulates cell proliferation and the release of multiple hormones via activation of its cognate receptors. A variety of SST analogs, some with high affinity and selectivity of receptor subtypes, have been synthesized and developed. Certain long-acting SST analogs such as octreotide, lanreotide and pasireotide have been clinically applied to the treatment of human diseases such as those caused by excessive release of growth hormone (acromegaly), or adrenocorticotropic hormone (Cushing's syndrome), and for the treatment of carcinoid syndrome. Investigations into new biological activities of these long-acting SSTs and their possible clinical applications are also still ongoing. Also, novel SST analogs are being designed and developed to target different receptor subtype(s) or mimic natural SST's multiple biological properties. Additionally, since SSTRs, especially SSTR2, are aberrantly expressed in many cancer cells and tumor blood vessels, internalizing SST analogs is currently being used as drug-delivery vehicle for the application of receptor-targeted therapeutics. This review will discuss recent advances in the development and applications of SST and its analogs.

Cervical cancer is a second leading cancer death in women world-wide, with most cases in less developed countries.Notch signaling is highly conserved with its involvement in many cancers.In the present study, we established stable cervical cell lines with Notch activation and inactivation and found that Notch activation played a suppressive role in cervical cancer cells.Meanwhile, the transient overexpression of the active intracellular domain of all four Notch receptors (ICN1, 2, 3, and 4) also induced the suppression of cervical cancer Hela cell growth.ICN1 also induced cell cycle arrest at phase G1.Notch1 signaling activation affected the expression of serial genes, especially the genes associated with cAMP signaling, with an increase of genes like THBS1, VCL, p63, c-Myc and SCG2, a decrease of genes like NR4A2, PCK2 and BCL-2.Particularly, The nuclear receptor NR4A2 was observed to induce cell proliferation via MTT assay and reduce cell apoptosis via FACS assay.Furthermore, NR4A2's activation could reverse ICN1-induced suppression of cell growth while erasing ICN1-induced increase of tumor suppressor p63.These findings support that Notch signaling mediates cervical cancer cell growth suppression with the involvement of nuclear receptor NR4A2.Notably, Notch/NR4A2/p63 signaling cascade possibly is a new signling pathway undisclosed.

Hepatocellular carcinoma (HCC) is one of the most malignant cancers, with the second highest cancer death rate world-wide, next to lung cancer. The signaling mechanisms in HCC are currently not clear. Notch signaling, which is highly conserved and plays a critical role in many cancers, was found to be aberrantly upregulated in HCC tissues compared to normal liver tissues. Accumulating evidence supports that Notch signaling plays a significantly important role in HCC carcinogenesis. This review discusses the functions of Notch signaling in HCC and its potential therapeutic applications against this cancer.

BACKGROUND:Human pancreatic carcinoids, a type of neuroendocrine tumors, are asymptomatic and difficult to diagnose, with the effects of traditional anti-cancer therapies being limited. The histone deacetylase (HDAC) inhibitor valproic acid (VPA) was evaluated for its effects alone and in combination with receptor-targeting peptide-drug conjugate via increasing drug internalization.MATERIALS AND METHODS:The in vitro and in vivo assays were used to evaluate the effects of VPA and somatostatin receptor-targeting camptothecin-somatostatin conjugate (CPT-SST).RESULTS:VPA induced proliferation suppression, cell apoptosis and cell cycle arrest. VPA acts as a HDAC inhibitor to induce a decrease of HDAC4 and an increase of acetylated histone 4 (AcH4). Meanwhile, most importantly, besides activating Notch signaling, VPA was observed to stimulate the expression of somatostatin receptor type 2 (SSTR2) that has been applied for receptor-targeting therapies. This characteristic was used for a combination therapy of VPA and CPT-SST. The combination displayed much more potent anti-tumor effects on carcinoid tumor growth by increasing SSTR2 density and drug internalization in target tumor cells.CONCLUSION:The combination of VPA and a SSTR2-targeting agent provides us a promising approach in treatment of carcinoid tumors.

Hepatocellular carcinoma (HCC) is a type of malignant cancer. Notch signaling is aberrantly expressed in HCC tissues with more evidence showing that this signaling plays a critical role in HCCs. In the present study, we investigate the effects of the anti-convulsant drug valproic acid (VPA) in HCC cells and its involvement in modulating Notch signaling. We found that VPA, acting as a histone deacetylase (HDAC) inhibitor, induced a decrease in HDAC4 and an increase in acetylated histone 4 (AcH4) and suppressed HCC cell growth. VPA also induced down-regulation of Notch signaling via suppressing the expression of Notch1 and its target gene HES1, with an increase of tumor suppressor p21 and p63. Furthermore, Notch1 activation via overexpressing Notch1 active form ICN1 induced HCC cell proliferation and anti-apoptosis, indicating Notch signaling played an oncogenic role in HCC cells. Meanwhile, VPA could reverse Notch1-induced increase of cell proliferation. Interestingly, VPA was also observed to stimulate the expression of G protein-coupled somatostatin receptor type 2 (SSTR2) that has been used in receptor-targeting therapies. This discovery supports a combination therapy of VPA with the SSTR2-targeting agents. Our in vitro assay did show that the combination of VPA and the peptide-drug conjugate camptothecin-somatostatin (CPT-SST) displayed more potent anti-proliferative effects on HCC cells than did each alone. VPA may be a potential drug candidate in the development of anti-HCC drugs via targeting Notch signaling, especially in combination with receptor-targeting cytotoxic agents.

This following article is written for Prof. Abba Kastin's Festschrift, to add to the tribute to his important role in the advancement of the role of peptides in physiological, as well as pathophysiological processes. There have been many advances during the 35 years of his prominent role in the Peptide field, not only as editor of the journal Peptides, but also as a scientific investigator and editor of two volumes of the Handbook of Biological Active Peptides [146], [147]. Similar to the advances with many different peptides, during this 35 year period, there have been much progress made in the understanding of the pharmacology, cell biology and the role of (bombesin) Bn receptors and their ligands in various disease states, since the original isolation of bombesin from skin of the European frog Bombina bombina in 1970 [76]. This paper will briefly review some of these advances over the time period of Prof. Kastin 35 years in the peptide field concentrating on the advances since 2007 when many of the results from earlier studies were summarized [128], [129]. It is appropriate to do this because there have been 280 articles published in Peptides during this time on bombesin-related peptides and it accounts for almost 5% of all publications. Furthermore, 22 Bn publications we have been involved in have been published in either Peptides [14], [39], [55], [58], [81], [92], [93], [119], [152], [216], [225], [226], [231], [280], [302], [309], [355], [361], [362] or in Prof. Kastin's Handbook of Biological Active Peptides [137], [138], [331].