CRISPR-Based Gene Therapies: From Preclinical to Clinical Treatments.

In recent years, clustered regularly interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (Cas) protein have emerged as a revolutionary gene editing tool to treat inherited disorders affecting different organ systems, such as blood and muscles. Both hematological and neuromuscular genetic disorders benefit from genome editing approaches but face different challenges in their clinical translation. The ability of CRISPR/Cas9 technologies to modify hematopoietic stem cells ex vivo has greatly accelerated the development of genetic therapies for blood disorders. In the last decade, many clinical trials were initiated and are now delivering encouraging results. The recent FDA approval of Casgevy, the first CRISPR/Cas9-based drug for severe sickle cell disease and transfusion-dependent ß-thalassemia, represents a significant milestone in the field and highlights the great potential of this technology. Similar preclinical efforts are currently expanding CRISPR therapies to other hematologic disorders such as primary immunodeficiencies. In the neuromuscular field, the versatility of CRISPR/Cas9 has been instrumental for the generation of new cellular and animal models of Duchenne muscular dystrophy (DMD), offering innovative platforms to speed up preclinical development of therapeutic solutions. Several corrective interventions have been proposed to genetically restore dystrophin production using the CRISPR toolbox and have demonstrated promising results in different DMD animal models. Although these advances represent a significant step forward to the clinical translation of CRISPR/Cas9 therapies to DMD, there are still many hurdles to overcome, such as in vivo delivery methods associated with high viral vector doses, together with safety and immunological concerns. Collectively, the results obtained in the hematological and neuromuscular fields emphasize the transformative impact of CRISPR/Cas9 for patients affected by these debilitating conditions. As each field suffers from different and specific challenges, the clinical translation of CRISPR therapies may progress differentially depending on the genetic disorder. Ongoing investigations and clinical trials will address risks and limitations of these therapies, including long-term efficacy, potential genotoxicity, and adverse immune reactions. This review provides insights into the diverse applications of CRISPR-based technologies in both preclinical and clinical settings for monogenic blood disorders and muscular dystrophy and compare advances in both fields while highlighting current trends, difficulties, and challenges to overcome.

CRISPR-Cas9 KO Cell Line Generation and Development of a Cell-Based Potency Assay for rAAV-FKRP Gene Therapy.

Limb-Girdle Muscular Dystrophy R9 (LGMDR9) is a dystroglycanopathy caused by Fukutin-related protein (FKRP) defects leading to the deficiency of α-DG glycosylation, essential to membrane integrity. Recombinant adeno-associated viral vector (rAAV) gene therapy offers great therapeutic promise for such neuromuscular disorders. Pre-clinical studies have paved the way for a phase 1/2 clinical trial aiming to evaluate the safety and efficacy of FKRP gene therapy in LGMDR9 patients. To demonstrate product activity, quality, and consistency throughout product and clinical development, regulatory authorities request several quality controls, including a potency assay aiming to demonstrate and quantify the intended biological effect of the gene therapy product. In the present study, we generated FKRP knock-out (KO) cells fully depleted of α-DG glycosylation using CRISPR-Cas9 to assess the functional activity of a rAAV-FKRP gene therapy. We then developed a high-throughput On-Cell-Western methodology to evaluate the restoration of α-DG glycosylation in KO-FKRP cells and determine the biological activity of the FKRP transgene. The determination of the half maximal effective concentration (EC50) provides a method to compare the rAAV-FKRP batch using a reference standard. The generation of KO-FKRP muscle cells associated with the high-throughput On-Cell-Western technique may serve as a cell-based potency assay to assess rAAV-FKRP gene therapy products.

CLDN1 Sensitizes Triple-Negative Breast Cancer Cells to Chemotherapy.

Triple-negative breast cancer (TNBC) is an aggressive subtype that constitutes 15-20% of breast cancer cases worldwide. Current therapies often evolve into chemoresistance and lead to treatment failure. About 77% of the TNBC lacks claudin-1 (CLDN1) expression, a major tight junction component, and this absence is correlated with poorer prognostic. Little is known about CLDN1 role on the chemosensitivity of breast cancer. Our clinical data analysis reveals that CLDN1 low expression is correlated to a poor prognostic in TNBC patients. Next, the sensitivity of various TNBC "claudin-1-high" or "claudin-1-low" cells to three compounds belonging to the main class of chemotherapeutic agents commonly used for the treatment of TNBC patients: 5-fluorouracil (5-FU), paclitaxel (PTX) and doxorubicin (DOX). Using RNA interference and stable overexpressing models, we demonstrated that CLDN1 expression increased the sensitivity of TNBC cell lines to these chemotherapeutic agents. Taken together, our data established the important role of CLDN1 in TNBC cells chemosensitivity and supported the hypothesis that CLDN1 could be a chemotherapy response predictive marker for TNBC patients. This study could allow new treatment protocols creation aimed to induce CLDN1 expression in TNBCs to increase their sensitivity to chemotherapy.

Skeletal Muscle Cells Derived from Induced Pluripotent Stem Cells: A Platform for Limb Girdle Muscular Dystrophies.

Limb girdle muscular dystrophies (LGMD), caused by mutations in 29 different genes, are the fourth most prevalent group of genetic muscle diseases. Although the link between LGMD and its genetic origins has been determined, LGMD still represent an unmet medical need. Here, we describe a platform for modeling LGMD based on the use of human induced pluripotent stem cells (hiPSC). Thanks to the self-renewing and pluripotency properties of hiPSC, this platform provides a renewable and an alternative source of skeletal muscle cells (skMC) to primary, immortalized, or overexpressing cells. We report that skMC derived from hiPSC express the majority of the genes and proteins that cause LGMD. As a proof of concept, we demonstrate the importance of this cellular model for studying LGMDR9 by evaluating disease-specific phenotypes in skMC derived from hiPSC obtained from four patients.

AB186 Inhibits Migration of Triple-Negative Breast Cancer Cells and Interacts with α-Tubulin.

Breast cancer is one of the leading causes of cancer-related death among females worldwide. A major challenge is to develop innovative therapy in order to treat breast cancer subtypes resistant to current treatment. In the present study, we examined the effects of two Troglitazone derivatives Δ2-TGZ and AB186. Previous studies showed that both compounds induce apoptosis, nevertheless AB186 was a more potent agent. The kinetic of cellular events was investigated by real-time cell analysis system (RTCA) in MCF-7 (hormone dependent) and MDA-MB-231 (triple negative) breast cancer (TNBC) cells, followed by cell morphology analysis by immuno-localization. Both compounds induced a rapid modification of both impedance-based signals and cellular morphology. This process was associated with an inhibition of cell migration measured by wound healing and transwell assays in TNBC MDA-MB-231 and Hs578T cells. In order to identify cytoplasmic targets of AB186, we performed surface plasmon resonance (SPR) and pull-down analyses. Subsequently, 6 cytoskeleton components were identified as potential targets. We further validated α-tubulin as one of the direct targets of AB186. In conclusion, our results suggested that AB186 could be promising to develop novel therapeutic strategies to treat aggressive forms of breast cancer such as TNBC.

Claudin 1 inhibits cell migration and increases intercellular adhesion in triple-negative breast cancer cell line.

Triple-negative "claudin 1 low" subtype represents around 15% of breast cancer and displays poor prognosis. The loss of claudin 1 is correlated with increased invasiveness and higher recurrence of the disease. Claudin 1 constitutes the backbone of the tight junction and is involved in cell-cell adhesion and migration processes. However, studies showed a controversial role of claudin 1 in cell migration. In this study, we aimed to clarify the effect of claudin 1 on migration of mesenchymal triple-negative breast cancer cells (TNBC). We reported that transient over expression of claudin 1 in MDA-MB-231 and Hs578T "claudin 1 low" TNBC cells inhibited cell migration using wound healing and transwell migration assays. In order to investigate more specifically the involvement of claudin 1, we generated stable MDA-MB-231 clones overexpressing claudin 1. Interestingly, the level of claudin 1 was correlated to the inhibition of cell migration and to the increase of cell-cell aggregation associated with enhanced formation of ß-catenin adherens junction and occludin tight junction. Finally, we reported for the first time the key role of claudin 1 in the inhibition of cell migration process associated with the disappearance of stress fibers. These data suggest that re-expression of claudin 1 could be a promising strategy for regulating the migration of TNBC which no longer express claudin 1.

Pro-apoptotic effect of Δ2-TGZ in "claudin-1-low" triple-negative breast cancer cells: involvement of claudin-1.

PURPOSE: 40% of triple-negative breast cancer (TNBC) do not express claudin-1, a major constituent of tight junction. Patients with these "claudin-1-low" tumors present a higher relapse incidence. A major challenge in oncology is the development of innovative therapies for such poor prognosis tumors. In this context, we study the anticancer effects of ∆2-TGZ, a compound derived from troglitazone (TGZ), on cell models of these tumors. METHODS AND RESULTS: In MDA-MB-231 and Hs578T "claudin-1-low" TNBC cells, Δ2-TGZ treatment induced claudin-1 protein expression and triggered apoptosis as measured by FACS analysis (annexin V/PI co-staining). Interestingly, in the non-tumorigenic human breast epithelial cell line MCF-10A, the basal level of claudin-1 was not modified following Δ2-TGZ treatment, which did not induce apoptosis. Furthermore, claudin-1-transfected MDA-MB-231 and Hs578T cells displayed a significant increase of cleaved PARP-1 and caspase 7, caspase 3/7 activities, and TUNEL staining. RNA interference was performed in order to inhibit Δ2-TGZ-induced claudin-1 expression in both the cells. In absence of claudin-1, a decrease of cleaved PARP-1 and caspase 7 and caspase 3/7 activities were observed in MDA-MB-231 but not in Hs578T cells. CONCLUSION: Claudin-1 overexpression and Δ2-TGZ treatment are associated to apoptosis in MDA-MB-231 and Hs578T "claudin-1-low" TNBC. Moreover, in MDA-MB-231 cells, claudin-1 is involved in the pro-apoptotic effect of Δ2-TGZ. Our results suggest that claudin-1 re-expression could be an interesting therapeutic strategy for "claudin-1-low" TNBC.

Reprofiling of Troglitazone Towards More Active and Less Toxic Derivatives: A New Hope for Cancer Treatment?

The existence of unresponsive tumors and the appearance of resistant tumors during the course of treatments both justify that we increase urgently the panel of pharmacological molecules able to fight cancer. An interesting strategy is drug reprofiling (also known as drug repositioning, drug repurposing or drug retasking) that consists of identifying and developing new uses for existing drugs. This review illustrates drug reprofiling with troglitazone (TGZ), a synthetic PPARγ agonist initially used for the treatment of type II diabetes. The fact that TGZ also displays anticancer effects is known since the end of the nineties but its development as an anticancer agent was slowed down due to hepatotoxic side effects. Part of the knowledge available for TGZ, mainly the molecular basis for PPARγ activation, its metabolization pathways and the side effects on hepatocytes, were taken into account to elaborate new molecules. Key findings were that unsaturated TGZ derivatives, when compared to TGZ, do not activate PPARγ, exhibit a higher efficiency on cancer cells and a lower toxicity towards hepatocytes. However, a weakness is that the mechanisms involved in the anticancer effects are still not completely understood and that the efficiency of such derivatives has not yet been completely studied in vivo. Data about this point should become available very soon from animal models and this will be a prerequisite to initiate clinical trials with these potential new anticancer drugs developed from a drug repurposing strategy.