α3 integrin-binding peptide-functionalized polymersomes loaded with volasertib for dually-targeted molecular therapy for ovarian cancer

Transferrin-guided intelligent nanovesicles augment the targetability and potency of clinical PLK1 inhibitor to acute myeloid leukemia

Acute myeloid leukemia (AML) remains a most lethal hematological malignancy, partly because of its slow development of targeted therapies compared with other cancers. PLK1 inhibitor, volasertib (Vol), is among the few molecular targeted drugs granted breakthrough therapy status for AML; however, its fast clearance and dose-limiting toxicity greatly restrain its clinical benefits. Here, we report that transferrin-guided polymersomes (TPs) markedly augment the targetability, potency and safety of Vol to AML. Vol-loaded TPs (TPVol) with 4% transferrin exhibited best cellular uptake, effective down-regulation of p-PLK1, p-PTEN and p-AKT and superior apoptotic activity to free Vol in MV-4-11 leukemic cells. Intravenous injection of TPVol gave 6-fold higher AUC than free Vol and notable accumulation in AML-residing bone marrow. The efficacy studies in orthotopic MV-4-11 leukemic model demonstrated that TPVol significantly reduced leukemic cell proportions in periphery blood, bone marrow, liver and spleen, effectively enhanced mouse survival rate, and impeded bone loss. This transferrin-guided nano-delivery of molecular targeted drugs appears to be an interesting strategy towards the development of novel treatments for AML.

Peptides for diagnosis and treatment of ovarian cancer

Ovarian cancer is the most deadly gynecologic malignancy, and its incidence is gradually increasing. Despite improvements after treatment, the results are unsatisfactory and survival rates are relatively low. Therefore, early diagnosis and effective treatment remain two major challenges. Peptides have received significant attention in the search for new diagnostic and therapeutic approaches. Radiolabeled peptides specifically bind to cancer cell surface receptors for diagnostic purposes, while differential peptides in bodily fluids can also be used as new diagnostic markers. In terms of treatment, peptides can exert cytotoxic effects directly or act as ligands for targeted drug delivery. Peptide-based vaccines are an effective approach for tumor immunotherapy and have achieved clinical benefit. In addition, several advantages of peptides, such as specific targeting, low immunogenicity, ease of synthesis and high biosafety, make peptides attractive alternative tools for the diagnosis and treatment of cancer, particularly ovarian cancer. In this review, we focus on the recent research progress regarding peptides in the diagnosis and treatment of ovarian cancer, and their potential applications in the clinical setting.

Lysosomal-mediated drug release and activation for cancer therapy and immunotherapy

The development of carrier systems that are able to transport and release therapeutics to target cells is an emergent strategy to treat cancer; however, they following endocytosis are usually trapped in the endo/lysosomal compartments. The efficacy of drug conjugates and nanotherapeutics relies critically on their intracellular drug release ability, for which advanced systems responding to the unique lysosomal environment such as acidic pH and abundant enzymes (e.g. cathepsin B, sulfatase and β-glucuronidase) or equipped with photochemical internalization property have been energetically pursued. In this review, we highlight the recent designs of smart systems that promote efficient lysosomal release and/or escape of anticancer agents including chemotherapeutics (e.g. doxorubicin, platinum, chloroquine and hydrochloroquine) and biotherapeutics (e.g. proteins, siRNA, miRNA, mRNA and pDNA) to cancer cells or immunotherapeutic agents (e.g. antigens, mRNA and immunoadjuvants) to antigen-presenting cells (APCs), thereby boosting cancer therapy and immunotherapy. Lysosomal-mediated drug release presents an appealing approach to develop innovative cancer therapeutics and immunotherapeutics.

HER-2-mediated nano-delivery of molecular targeted drug potently suppresses orthotopic epithelial ovarian cancer and metastasis

The treatment of epithelial ovarian cancer (EOC) has made slow progress due to absence of effective adjuvant chemotherapy that is capable of preventing tumor relapse and metastasis. Molecular targeted drugs such as PARP and PLK1 inhibitors appear to be promising new treatments for EOC. The low EOC cell uptake, poor selectivity and pronounced toxicity, however, greatly compromise their clinical efficacy. Herein, we report that HER-2-mediated nano-delivery of clinical PLK1-targeted drug, volasertib (Vol), while causing little toxicity potently suppresses orthotopic EOC and metastasis. Anti-HER-2 antibody, trastuzumab (Tra), was conjugated onto Vol-loaded polymersomes via click chemistry yielding Tra-PVol with a size of 33 nm and optimally about 5 Tra per polymersome. Tra-PVol exhibited clearly stronger uptake and anti-tumor activity (IC₅₀ = 59 nM) in HER-2 overexpressing SKOV-3 cells than free Vol and non-targeted PVol controls. Both biodistribution and therapeutic studies in orthotopic SKOV-3-Luc tumor-bearing mice displayed that Tra-PVol induced significantly better tumor deposition and retardation than PVol and that intraperitoneal administration outperformed intravenous administration. More interestingly, Tra-PVol was shown to effectively suppress the intraperitoneal metastasis and to markedly prolong the survival time of SKOV-3-Luc tumor-bearing mice. This HER-2 directed molecular therapy emerges as a potential treatment strategy toward EOC.

Folate-mediated targeted PLK1 inhibition therapy for ovarian cancer: A comparative study of molecular inhibitors and siRNA therapeutics

PLK1 is a promising target for clinical treatment of diverse malignancies including ovarian cancer (OC), in which PLK1 over-expression is often correlated with poor prognosis and short survival. PLK1 can be blocked with small molecular inhibitors like volasertib (Vol) or silenced with PLK1-specific siRNA (siPLK1), hence effectively suppressing tumor growth. Surprisingly, despite intensive work on molecular inhibitor and siRNA therapeutics, there is no direct comparison between them reported for targeted tumor therapy. Herein, we employing folate as a ligand and polymersomes as a nanovehicle performed a comparative study on Vol and siPLK1 in inhibiting OC in vitro and in vivo. Folate-targeted polymersomal Vol and siPLK1 (termed as FA-Ps-Vol and FA-Ps-siPLK1, respectively) were both nano-sized and stable, and displayed an optimal FA density of 20% for SKOV-3 cells. Notably, FA-Ps-Vol and FA-Ps-siPLK1 exhibited an IC₅₀ of 193 and 770 nM, respectively, to SKOV-3 cells, indicating a greater potency of Vol than siPLK1. The markedly increased uptake for FA-Ps-Vol and FA-Ps-siPLK1 compared with respective non-targeted controls by SKOV-3 tumor xenografts in mice confirmed that FA mediates strong OC-targeting in vivo. Intriguingly, FA-Ps-Vol while greatly lessening toxic effects of Vol potently repressed tumor growth with a remarkable tumor inhibition rate (TIR) of 97% at 20 mg (i.e. 32.4 µmol) Vol equiv./kg. FA-Ps-siPLK1 achieved effective tumor inhibition (TIR = ca. 87% or 90%) at 2 or 4 mg (i.e. 0.15 or 0.3 µmol) siPLK1 equiv./kg without causing adverse effects. This comparative study highlights that molecular inhibitor has the advantage of easy dose escalation and potent protein inhibition at the expense of certain adverse effects while siRNA therapeutics has low toxicity with moderate protein inhibition in vivo. STATEMENT OF SIGNIFICANCE: PLK1 is a promising target for the development of innovative and specific treatments against diverse malignancies. Interestingly, despite intensive work on molecular inhibitors and siRNA against PLK1, little work has been directed to compare their efficacy in targeted tumor therapy. Here, we employed folate as a ligand and polymersomes as a nanovehicle and have performed a comparative study on volasertib and siPLK1 in inhibiting ovarian cancer in vitro and in vivo. Our data show that the dose of volasertib can be easily escalated to induce prominent antitumor efficacy at the expense of certain adverse effects, while siPLK1 brings about moderate protein inhibition and antitumor therapy without causing toxicity at two-orders-of-magnitude lower dose.

Emerging targeted drug delivery strategies toward ovarian cancer

Ovarian cancer is a high-mortality malignancy in women. The contemporary clinical chemotherapy with classic cytotoxic drugs, targeted molecular inhibitors would mostly fail when ovarian cancer cells become drug-resistant or metastasize through the body or when patients bare no more toleration because of strong adverse effects. The past decade has spotted varying targeted delivery systems including antibody-drug conjugates (ADCs), peptide/folate/aptamer-drug conjugates, polymer-drug conjugates, ligand-functionalized nanomedicines, and dual-targeted nanomedicines that upgrade ovarian cancer chemo- and molecular therapy effectively in preclinical/clinical settings via endowing therapeutic agents selectivity and bypassing drug resistance as well as lessening systemic toxicity. The targeted delivery approaches further provide means to potentiate emergent treatment modalities such as molecular therapy, gene therapy, protein therapy, photodynamic therapy, dual-targeting therapy and combination therapy for ovarian cancer. This review highlights up-to-date development of targeted drug delivery strategies toward advanced, metastatic, relapsed, and drug resistant ovarian cancers.

Strategies for active tumor targeting-an update

A complete cure for cancer is still the holy grail for scientists. The existing treatment of cancer is primarily focused on surgery, radiation and conventional chemotherapy. However, chemotherapeutic agents also affect healthy tissues or organs due to a lack of specificity. While passive targeting is studied for anticancer drugs focused on the enhanced permeability and retention effect, it failed to achieve drug accumulation at the tumor site and desired therapeutic efficacy. This review presents an outline of the current significant targets for active tumor drug delivery systems and provides insight into the direction of active tumor-targeting strategies. For this purpose, a systematic understanding of the physiological factors, tumor microenvironment and its components, overexpressed receptor and associated proteins are covered here. We focused on angiogenesis mediated targeting, receptor-mediated targeting and peptide targeting. This active targeting along with integration with nano delivery systems helps in achieving specific action, thus reducing the associated adverse effects to healthy tissues. Although the tumor-targeting methods and possibilities explored so far seem revolutionary in cancer treatment, in-depth clinical studies data is required for its commercial translation.

Synthesis of zwitterionic chimeric polymersomes for efficient protein loading and intracellular delivery

Design and synthesis of degradable chimeric polymersomes based on zwitterionic PAC(DMA)-PCL-PMDMSA triblock copolymers for high protein loading and intracellular delivery.