Solution structure of a synthetic peptide corresponding to a receptor binding region of FSH (hFSH-beta 33-53)

Synthesis, characterization and multi-spectroscopic DNA/HSA interaction studies of synthetic human Follicle-Stimulating Hormone Beta 33-53 peptide conjugated PEGylated graphene oxide nanoparticles

The objective of the current study was to synthesize, characterize and explore the interaction of PEGylated graphene oxide (pGO) and synthetic human Follicular stimulating hormone β 33-53 peptide conjugated PEGylated graphene oxide nanoparticles (pGO-FSH) with human serum albumin (HSA) and calf thymus DNA (CT-DNA). The pGO/ pGO-FSH nanoparticles were synthesized using a modified Hummer's method, and the FSH peptide was conjugated through a maleimide crosslinking reaction. Synthesized nanoparticles were then characterized using techniques like FT-IR, UV-Visible absorbance, CD and Raman spectroscopy, and XRD and TGA. Morphological and particle size analysis was studied using SEM, TEM, DLS, and zeta potential measurements. The presence of FSH β 33-53 peptide was confirmed qualitatively and quantitatively using CD spectroscopy and Bradford's assay. Binding studies of pGO/pGO-FSH nanoparticles with HSA and DNA were carried out using biophysical techniques. The complex formation between pGO/pGO-FSH nanoparticles and HSA was revealed by UV absorbance spectroscopy, and the observed fluorescence quenching was confirmed by steady-state fluorescence spectroscopy. Time-resolved fluorescence quenching studies have shown that dynamic quenching plays an important role in binding HSA with pGO/pGO-FSH nanoparticles. However, structurally no significant changes were observed in the native structure of HSA upon binding with pGO/pGO-FSH nanoparticles suggesting that the latter did not induce any structural distortions together, confirmed by DSC, FT-IR, and CD spectroscopy experimental findings. Binding constants and thermodynamic parameters calculated using double logarithmic and Van't Hoff plots suggested weak and moderate binding affinity along with the involvement of hydrophobic and hydrogen bonding interactions between HSA and pGO/pGO-FSH nanoparticles, respectively. UV absorbance and fluorescence spectroscopy have revealed that pGO/pGO-FSH nanoparticles interact with DNA by binding at the minor groove region. These findings were further confirmed by DNA melting and viscosity studies. CD and FT-IR spectroscopy studies have shown no changes in the helical structure of B-form of DNA, thereby emphasizing the groove-binding nature of pGO/pGO-FSH nanoparticles. The obtained results are useful in further considering the potentiality of pGO-FSH nanoparticles as drug-delivery systems for in vivo applications, especially to target ovarian cancer.

Peptide-Based Vectors: A Biomolecular Engineering Strategy for Gene Delivery

From the first clinical trial by Dr. W.F. Anderson to the most recent US Food and Drug Administration-approved Luxturna (Spark Therapeutics, 2017) and Zolgensma (Novartis, 2019), gene therapy has revamped thinking and practice around cancer treatment and improved survival rates for adult and pediatric patients with genetic diseases. A major challenge to advancing gene therapies for a broader array of applications lies in safely delivering nucleic acids to their intended sites of action. Peptides offer unique potential to improve nucleic acid delivery based on their versatile and tunable interactions with biomolecules and cells. Cell-penetrating peptides and intracellular targeting peptides have received particular focus due to their promise for improving the delivery of gene therapies into cells. We highlight key examples of peptide-assisted, targeted gene delivery to cancer-specific signatures involved in tumor growth and subcellular organelle-targeting peptides, as well as emerging strategies to enhance peptide stability and bioavailability that will support long-term implementation.

Optimizing the performance of 68Ga labeled FSHR ligand in Prostate Cancer Model by Co-Administration of Aprotinin

PURPOSE

Radiolabeled FSH1 peptides are potential specific probes for FSHR imaging. However, moderate uptakes and fast washout from the tumors may limit its widespread use. In this study, ⁶⁸Ga labeled modified FSH1 analogs was prepared and the imaging properties were determined in the prostate cancer model with or without aprotinin.

METHODS

NOTA-MAL-FSH4 was synthesized and labeled with ⁶⁸Ga. The pharmacokinetic profile of the peptide after co-administration with aprotinin was determined through metabolism analyses and microPET imaging.

RESULTS

⁶⁸Ga-NOTA-MAL-FSH4 was successfully prepared. The IC50 value of displacement ⁶⁸Ga-NOTA-MAL-FSH4 with FSH1 was 139.4 ± 1.16 nM. The PC-3 prostate tumor was visible after administration of the ⁶⁸Ga labeled tracer. In vitro RP-HPLC analysis revealed that the average percentage of intact peptide in the plasma, liver and tumor was 8.30, 9.57 and 7.06% respectively. In presence of aprotinin, the amounts of intact peptide increased to 34.32%, 20.63% and 15.39% in the counterparts respectively. MicroPET imaging showed that the uptakes of PC-3 tumors at 60mins after co-administration of 100μg, 200μg or 400μg enzyme inhibitors were 2.91 ± 0.21%ID/g, 3.89 ± 0.16%ID/g and 9.21 ± 0.22%ID/g respectively.

CONCLUSION

With the aid of a serine protease inhibitor, the performance of the ⁶⁸Ga labeled peptide was optimized, which may benefit further clinical application.

A Comprehensive Review of Non-Covalent Radiofluorination Approaches Using Aluminum [18F]fluoride: Will [18F]AlF Replace 68Ga for Metal Chelate Labeling?

Due to its ideal physical properties, fluorine-18 turns out to be a key radionuclide for positron emission tomography (PET) imaging, for both preclinical and clinical applications. However, usual biomolecules radiofluorination procedures require the formation of covalent bonds with fluorinated prosthetic groups. This drawback makes radiofluorination impractical for routine radiolabeling, gallium-68 appearing to be much more convenient for the labeling of chelator-bearing PET probes. In response to this limitation, a recent expansion of the 18F chemical toolbox gave aluminum [18F]fluoride chemistry a real prominence since the late 2000s. This approach is based on the formation of an [18F][AlF]2+ cation, complexed with a 9-membered cyclic chelator such as NOTA, NODA or their analogs. Allowing a one-step radiofluorination in an aqueous medium, this technique combines fluorine-18 and non-covalent radiolabeling with the advantage of being very easy to implement. Since its first reports, [18F]AlF radiolabeling approach has been applied to a wide variety of potential PET imaging vectors, whether of peptidic, proteic, or small molecule structure. Most of these [18F]AlF-labeled tracers showed promising preclinical results and have reached the clinical evaluation stage for some of them. The aim of this report is to provide a comprehensive overview of [18F]AlF labeling applications through a description of the various [18F]AlF-labeled conjugates, from their radiosynthesis to their evaluation as PET imaging agents.

Targeting Membrane Receptors of Ovarian Cancer Cells for Therapy

Ovarian cancer is a leading cause of death worldwide from gynecological malignancies, mainly because there are few early symptoms and the disease is generally diagnosed at an advanced stage. In addition, despite the effectiveness of cytoreductive surgery for ovarian cancer and the high response rates to chemotherapy, survival has improved little over the last 20 years. The management of patients with ovarian cancer also remains similar despite studies showing striking differences and heterogeneity among different subtypes. It is therefore clear that novel targeted therapeutics are urgently needed to improve clinical outcomes for ovarian cancer. To that end, several membrane receptors associated with pivotal cellular processes and often aberrantly overexpressed in ovarian cancer cells have emerged as potential targets for receptor-mediated therapeutic strategies including specific agents and multifunctional delivery systems based on ligand-receptor binding. This review focuses on the profiles and potentials of such strategies proposed for ovarian cancer treatment and imaging.

An Investigation on a Novel Anti-tumor Fusion Peptide of FSH33-53-IIKK

A novel fusion peptide FSH_33-53-IIKK was designed and expected to combine the follicle stimulating hormone receptor (FSHR) targeting and tumor toxicity. In vitro and in vivo study showed the anti-tumor activity of FSH_33-53-IIKK was enhanced compared to that of IIKK only. FSH_33-53-IIKK could inhibit the growth of tumor via apoptosis and autophagy pathways. In summary, combining the tumor marker-target peptide and anti-tumor peptide together may be an efficient way to search for better anti-tumor candidates.

The potential of follicle-stimulating hormone peptide-modified triptolide-loaded nanoparticles to induce a mouse model of premature ovarian insufficiency

The use of triptolide (TP) is limited by its poor water solubility and severe toxicity. In this study, we developed an active drug delivery system (TP-loaded nanoparticles) that could help improve the water solubility of TP and decrease its toxicity. Then, we investigated whether TP-loaded nanoparticles could be used to establish a novel premature ovarian insufficiency mouse model. The mice treated with TP-loaded nanoparticles for 35 days displayed normal growth, decreased serum antimullerian hormone, prominent ovarian fibrosis and vacuolar changes, fewer follicles and corpus lutea, increased collapsed oocytes and follicle apoptosis, and sterility. In conclusion, this model appears to show the reproductive characteristics associated with premature ovarian insufficiency in women and will allow us to study the mechanism of the effects of traditional Chinese medicine on gonadal toxicity.

Pilot study of a novel (18)F-labeled FSHR probe for tumor imaging

PURPOSE

Follicle-stimulating hormone receptor (FSHR) is overexpressed in primary and metastatic tumor. Molecular imaging of FSHR is beneficial for prognosis and therapy of cancer. FSHβ(33-53) (YTRDLVYKDPARPKIQKTCTF), denoted as FSH1, is a FSHR antagonist. In the present study, maleimide-NOTA conjugate of FSH1 (NOTA-MAL-FSH1) was designed and labeled with [(18)F] aluminum fluoride. The resulting tracer, (18)F-Al-NOTA-MAL-FSH1, was preliminarily evaluated in PET imaging of FSHR-positive tumor.

PROCEDURES

NOTA-MAL-FSH1 was synthesized and radiolabeled with Al(18)F complex. The tumor-targeting potential and pharmacokinetic profile of the (18)F-labeled compound were evaluated in vitro and in vivo using a PC3 human prostate tumor model.

RESULTS

(18)F-Al-NOTA-MAL-FSH1 can be efficiently produced within 30 min with a non-decay-corrected yield of 48.6 ± 2.1 % and a radiochemical purity of more than 95 %. The specific activity was at least 30 GBq/μmol. The radiotracer was stable in phosphate-buffered saline and human serum for at least 2 h. The IC50 values of displacement (18)F-Al-NOTA-MAL-FSH1 with FSH1 were 252 ± 1.12 nM. The PC3 human prostate tumor xenografts were clearly visible with high contrast after injection of (18)F-Al-NOTA-MAL-FSH1 via microPET. At 30, 60 and 120 min postinjection, the tumor uptakes were 2.98 ± 0.29 % injected dose (ID)/g, 2.53 ± 0.20 %ID/g and 1.36 ± 0.12 %ID/g, respectively. Dynamic PET scanning showed that tumor uptake reached a plateau by about 6 min. Heart peaked earlier and then cleared quickly. Biodistribution studies confirmed that the normal organs except kidney uptakes were all below 1 %ID/g at 1 h p.i. The tumor-to-blood and tumor-to-muscle ratio at 10 min, 0.5, 1, and 2 h after injection were 1.64 ± 0.36, 2.97 ± 0.40, 9.31 ± 1.06, and 13.59 ± 2.33 and 7.05 ± 1.10, 10.10 ± 1.48, 16.17 ± 3.29, and 30.88 ± 4.67, respectively. The tracer was excreted mainly through the renal system, as evidenced by high levels of radioactivity in the kidneys. FSHR-binding specificity was also demonstrated by reduced tumor uptake of (18)F-Al-NOTA-MAL-FSH1 after coinjection with an excess of unlabeled FSH1 peptide.

CONCLUSION

NOTA-MAL-FSH1 could be labeled rapidly and efficiently with (18)F using one step method. Favorable preclinical data suggest that (18)F-Al-NOTA-MAL-FSH1 may be a suitable radiotracer for the non-invasive visualization of FSHR positive tumor in vivo.

Targeting of follicle stimulating hormone peptide-conjugated dendrimers to ovarian cancer cells

Ovarian cancer is the most lethal gynecological malignancy. Current treatment modalities include a combination of surgery and chemotherapy, which often lead to loss of fertility in premenopausal women and a myriad of systemic side effects. To address these issues, we have designed poly(amidoamine) (PAMAM) dendrimers to selectively target the follicle stimulating hormone receptor (FSHR), which is overexpressed by tumorigenic ovarian cancer cells but not by immature primordial follicles and other non-tumorigenic cells. Fluorescein-labeled generation 5 (G5) PAMAM dendrimers were conjugated with the binding peptide domain of FSH (FSH33) that has a high affinity to FSHR. The targeted dendrimers exhibited high receptor selectivity to FSHR-expressing OVCAR-3 cells, resulting in significant uptake and downregulation of an anti-apoptotic protein survivin, while showing minimal interactions with SKOV-3 cells that do not express FSHR. The selectivity of the FSH33-targeted dendrimers was further validated in 3D organ cultures of normal mouse ovaries. Immunostaining of the conjugates revealed their selective binding and uptake by ovarian surface epithelium (OSE) cells that express FSHR, while sparing the immature primordial follicles. In addition, an in vivo study monitoring tissue accumulation following a single intraperitoneal (i.p.) injection of the conjugates showed significantly higher accumulation of FSH33-targeted dendrimers in the ovary and oviduct compared to the non-targeted conjugates. These proof-of-concept findings highlight the potential of these FSH33-targeted dendrimers to serve as a delivery platform for anti-ovarian cancer drugs, while reducing their systemic side effects by preventing nonspecific uptake by the primordial follicles.

Follicle-stimulating hormone peptide can facilitate paclitaxel nanoparticles to target ovarian carcinoma in vivo

Chemotherapy is an important treatment for ovarian cancer. However, conventional chemotherapy has inevitable drawbacks due to side effects from nonspecific biodistribution of the chemotherapeutic drugs. To solve such problem, targeted delivery approaches were developed. The targeted delivery approaches combine drug carriers with the targeting system and can preferentially bring drugs to the targeted sites. Follicle-stimulating hormone receptor (FSHR) is an ovarian cancer-specific receptor. By using a peptide derived from FSH (amino acids 33-53 of the FSH beta chain, named as FSH33), we developed a conjugated nanoparticle, FSH33-NP, to target FSHR in ovarian cancer. FSH33-NP was tested for recognition specificity and uptake efficiency on FSHR-expressing cells. Then, the antitumor efficiency of paclitaxel (PTX)-loaded FSH33-NP (FSH33-NP-PTX) was determined. FSH33-NP-PTX displayed stronger antiproliferation and antitumor effects compared with free PTX or naked PTX-loaded nanoparticles (NP-PTX) both in vitro and in vivo. In summary, this novel FSH33-NP delivery system showed very high selectivity and efficacy for FSHR-expressing tumor tissues. Therefore, it has good potential to become a new therapeutic approach for patients with ovarian cancer.

Analysis of glycoprotein hormone receptor extracellular domain interactions using a solid-phase capture assay

The receptors for the glycoprotein hormones are unique in having a large extracellular domain that is responsible for mediating ligand binding. We describe the characterization, validation, and application of a solid-phase radioligand binding assay that can be used to assess the interaction of peptides and small molecules at the extracellular domain (ECD) of the follicle-stimulating hormone receptor (FSHR). The assay utilizes a C-terminal tag on the FSHR-ECD, which is used to capture the ECD and position it in a sterically favorable orientation on a solid-phase platform. Competition experiments with the cognate ligand, FSH, indicated that the interaction at the FSHR-ECD using the solid-phase assay was comparable to the full-length receptor assayed using a standard filtration assay. The utility of the assay was evaluated by competing several peptides and a small molecule for both the full-length FSHR and the FSHR-ECD. The solid-phase capture format allowed for the establishment of an assay to specifically evaluate compounds that interact at the ECD or require the full-length receptor, thereby facilitating structure-activity studies. This assay format should be applicable to the other receptors of this family.

Scanning-alanine mutagenesis of long loop residues 33-53 in follicle stimulating hormone beta subunit

Follicle stimulating hormone (FSH) is a gonadotropin and member of the pituitary/placental glycoprotein hormone family which bind to G-protein-coupled receptors. These hormones are heterodimers composed of a common alpha and distinct beta -subunits. Previous experimental evidence suggested that the FSH beta -subunit long loop comprised of amino acids Tyr33 to Phe53 is involved in receptor binding and activation and in subunit interaction. According to recently reported crystal structures of human chorionic gonadotropin (hCG), the homologous long loop of the beta -subunit of hCG associates with the alpha -subunit and is partially exposed to solvent. This report describes the results of scanning alanine mutagenesis used to determine if amino acid side chains in this region of the molecule are required for receptor binding and/or subunit contact. Five mutations were made which spanned this loop and the mutant FSH beta-subunits were co-expressed with alpha-subunit in a Baculovirus-infected insect-cell expression system. Mutation of 48QKTCT52 to 48AAACA52 produced a FSH beta-subunit that failed to form heterodimer, consistent with the crystal structure of hCG which shows these amino acids are buried at the subunit interface. The four remaining mutants produced heterodimer and were assayed for binding to and activation of human FSH receptors. Mutation of 37LVY39 to 37AAA39 caused a 20-fold reduction binding (ID50 of 7.0 nM compared with 0.3 nM for wildtype). Mutation of 34TRDL37 to 34AAAA37 or 44RPKI47 to 44APAA47 caused lesser but measurable effects with ID50 values of 1.1 nM and 1.9 nM, respectively. The (40)KDPA(43) to 40KDPA43 to 40AAPA43 mutation had little effect on receptor binding (ID50 = 0.5 nM).