Targeting Tn-Antigen-Positive Human Tumors with a Recombinant Human Macrophage Galactose C-Type Lectin.

Alterations in glycosylation cause the emergence of tumor-associated carbohydrate antigens (TACAs) during tumorigenesis. Truncation of O-glycans reveals the Thomsen nouveau (Tn) antigen, an N-acetylgalactosamine (GalNAc) frequently attached to serine or threonine amino acids, that is accessible on the surface of cancer cells but not on healthy cells. Interestingly, GalNac can be recognized by macrophage galactose lectin (MGL), a type C lectin receptor expressed in immune cells. In this study, recombinant MGL fragments were tested in vitro for their cancer cell-targeting efficiency by flow cytometry and confocal microscopy and in vivo after administration of fluorescent MGL to tumor-bearing mice. Our results demonstrate the ability of MGL to target Tn-positive human tumors without inducing toxicity. This outcome makes MGL, a fragment of a normal human protein, the first vector candidate for in vivo diagnosis and imaging of human tumors and, possibly, for therapeutic applications.

Systemic Delivery of Tumor-Targeted Bax-Derived Membrane-Active Peptides for the Treatment of Melanoma Tumors in a Humanized SCID Mouse Model.

Melanoma is a highly metastatic and deadly form of cancer. Invasive melanoma cells overexpress integrin αvß3, which is a well-known target for Arg-Gly-Asp-based (RGD) peptides. We developed a sophisticated method to synthetize milligram amounts of a targeted vector that allows the RGD-mediated targeting, internalization, and release of a mitochondria-disruptive peptide derived from the pro-apoptotic Bax protein. We found that 2.5 µM Bax[109-127] was sufficient to destabilize the mitochondria in ten different tumor cell lines, even in the presence of the anti-apoptotic Bcl2 protein, which is often involved in tumor resistance. This pore-forming peptide displayed antitumor activity when it was covalently linked by a disulfide bridge to the tetrameric RAFT-c[RGD]4-platform and after intravenous injection in a human melanoma tumor model established in humanized immuno-competent mice. In addition to its direct toxic effect, treatment with this combination induced the release of the immuno-stimulating factor monocyte chimoattractant protein 1 (MCP1) in the blood and a decrease in the level of the pro-angiogenic factor FGF2. Our novel multifunctional, apoptosis-inducing agent could be further customized and assayed for potential use in tumor-targeted therapy.

Targeting CD44 receptor-positive lung tumors using polysaccharide-based nanocarriers: Influence of nanoparticle size and administration route.

New approaches that are more efficient and able to specifically reach lung tumors are needed. We developed new hyaluronan-based nanoparticles targeting CD44 receptors of two different sizes and compared their lung cancer cells targeting efficacy in vitro and in vivo. The nanoparticles' cellular uptake was dose-dependent, and specific to hyaluronan receptors, particularly CD44. The binding and internalization differed according to nanoparticle size. In vivo biodistribution studies in two orthotopic lung tumor models showed that intrapulmonary nebulized nanoparticles accumulated in lungs, but not in the tumor nodules. In contrast, despite a significant liver capture, intravenous injection led to a better accumulation of the nanoparticles in the lung tumors compared with the surrounding healthy lung tissues. We demonstrated that the hyaluronan-based nanoparticles size plays significant role in cellular uptake and biodistribution. Small nanoparticles showed active targeting of CD44-overexpressing tumors, suggesting that they could be used as drug-delivery system. FROM THE CLINICAL EDITOR: Combating cancers remains an important goal in clinical medicine. In this study, the authors investigated the ability of two hyaluronan-based nanoparticles targeting CD44 receptors to home in on lung cancer cells in an in-vivo orthotropic model. The preferential uptake of smaller sized nanoparticles via intravenous route has further enhanced the existing knowledge of future drug designs.

Role of near-infrared fluorescence imaging in head and neck cancer surgery: from animal models to humans.

Complete resection of head and neck cancers with negative surgical margins improves the prognosis of the disease and decreases the recurrence rate. Near-infrared fluorescence-guided surgery of head and neck cancer is a rapidly evolving field that represents an invaluable tool for tumor detection and resection. Here, we present a literature review of the principles of near-infrared fluorescence imaging and its use in head and neck cancer surgery. We discuss important studies in both animal models and humans that have been carried out up to this point. We also outline the important fluorescent molecules and devices used in head and neck fluorescence imaging-guided surgery. Although near-infrared fluorescence-guided surgery for head and neck cancers showed efficacy in animal models, its use in humans is limited by the small number of fluorescent probes that are approved for clinical use. However, it is considered as a novel surgical aid that helps delineate tumor margins preoperatively and could spare patients from the added morbidity that is associated with additional surgery or chemoradiation. In addition, it is a useful tool to detect sentinel lymph nodes as well as metastatic lymph nodes.

The PI3K/AKT pathway promotes gefitinib resistance in mutant KRAS lung adenocarcinoma by a deacetylase-dependent mechanism.

To select the appropriate patients for treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), it is important to gain a better understanding of the intracellular pathways leading to EGFR-TKI resistance, which is a common problem in patients with lung cancer. We recently reported that mutant KRAS adenocarcinoma is resistant to gefitinib as a result of amphiregulin and insulin-like growth factor-1 receptor overexpression. This resistance leads to inhibition of Ku70 acetylation, thus enhancing the BAX/Ku70 interaction and preventing apoptosis. Here, we determined the intracellular pathways involved in gefitinib resistance in lung cancers and explored the impact of their inhibition. We analyzed the activation of the phosphatidyl inositol-3-kinase (PI3K)/AKT pathway and the mitogen-activated protein kinase/extracellular-signal regulated kinase (MAPK/ERK) pathway in lung tumors. The activation of AKT was associated with disease progression in tumors with wild-type EGFR from patients treated with gefitinib (phase II clinical trial IFCT0401). The administration of IGF1R-TKI or amphiregulin-directed shRNA decreased AKT signaling and restored gefitinib sensitivity in mutant KRAS cells. The combination of PI3K/AKT inhibition with gefitinib restored apoptosis via Ku70 downregulation and BAX release from Ku70. Deacetylase inhibitors, which decreased the BAX/Ku70 interaction, inhibited AKT signaling and induced gefitinib-dependent apoptosis. The PI3K/AKT pathway is thus a major pathway contributing to gefitinib resistance in lung tumors with KRAS mutation, through the regulation of the BAX/Ku70 interaction. This finding suggests that combined treatments could improve the outcomes for this subset of lung cancer patients, who have a poor prognosis.

The multiple roles of amphiregulin in human cancer.

Amphiregulin (AREG) is one of the ligands of the epidermal growth factor receptor (EGFR). AREG plays a central role in mammary gland development and branching morphogenesis in organs and is expressed both in physiological and in cancerous tissues. Various studies have highlighted the functional role of AREG in several aspects of tumorigenesis, including self-sufficiency in generating growth signals, limitless replicative potential, tissue invasion and metastasis, angiogenesis, and resistance to apoptosis. The oncogenic activity of AREG has already been described in the most common human epithelial malignancies, such as lung, breast, colorectal, ovary and prostate carcinomas, as well as in some hematological and mesenchymal cancers. Furthermore, AREG is also involved in resistance to several cancer treatments. In this review, we describe the various roles of AREG in oncogenesis and discuss its translational potential, such as the development of anti-AREG treatments, based on AREG activity. In the last decade, independent groups have reported successful but sometimes contradictory results in relation to the potential of AREG to serve as a prognostic and/or predictive marker for oncology, especially with regard to anti-EGFR therapies. Thus, we also discuss the potential usefulness of using AREG as a therapeutic target and validated biomarker for predicting cancer outcomes or treatment efficacy.

Insulin-like growth factor-1 receptor inhibition overcomes gefitinib resistance in mucinous lung adenocarcinoma.

The appropriate selection of patients is a major challenge in the treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs). Prospective trials in adenocarcinoma demonstrated that the mucinous subtype presents a poorer outcome under EGFR-TKI treatment than the non-mucinous subtype. Our aim was to determine the molecular characteristics associated with resistance to EGFR-TKIs in mucinous and non-mucinous adenocarcinoma. Eighty adenocarcinoma samples, including 34 tumours from patients treated with gefitinib in a phase II clinical trial (IFCT0401), were classified as mucinous (n = 32) or non-mucinous (n = 48) adenocarcinoma. We demonstrated that four biological markers were differentially expressed between the two subtypes: mucinous tumours that overexpressed IGF1R (p < 0.0001) and amphiregulin (p = 0.004) with a tendency for more frequent KRAS mutations, in contrast to non-mucinous tumours that overexpressed EGFR (p < 0.0001) and TTF-1 (p < 0.0001) with more frequent EGFR mutations (p = 0.037). Higher IGF1R (p = 0.02) and lower TTF-1 (p = 0.02) expression was associated with disease progression under gefitinib treatment. We observed in vitro cross-talk between EGFR and IGF1R signalling pathways in gefitinib-resistant H358 mucinous cells. Anti-amphiregulin siRNAs and anti-IGF1R treatments sensitized the H358 cells to gefitinib-induced apoptosis with additive effects, suggesting that these treatments could overcome the resistance of mucinous tumours to EGFR-TKIs, including those with KRAS mutation. Our results highlighted that mucinous and non-mucinous adenocarcinoma subtypes are different entities with different therapeutic responses to EGFR-TKIs. These data will foster the development of therapeutic strategies for treating adenocarcinoma with mucinous component.

Tumor-Specific Imaging with Angiostamp800 or Bevacizumab-IRDye 800CW Improves Fluorescence-Guided Surgery over Indocyanine Green in Peritoneal Carcinomatosis.

Complete surgical removal of lesions improves survival of peritoneal carcinomatosis and can be enhanced by intraoperative near-infrared fluorescence imaging. Indocyanine green (ICG) is the only near-infrared fluorescent dye approved for clinical use, but it lacks specificity for tumor cells, highlighting the need for tumor-selective targeting agents. We compared the tumor-specific near-infrared fluorescent probes Bevacizumab-IRDye 800CW and Angiostamp800, which target tumor angiogenesis and cancer cells, to ICG for fluorescence-guided surgery in peritoneal carcinomatosis of ovarian origin. The probes were administered to mice with orthotopic peritoneal carcinomatosis prior to conventional and fluorescence-guided surgery. The influence of neoadjuvant chemotherapy was also assessed. Conventional surgery removed 88.0 ± 1.2% of the total tumor load in mice. Fluorescence-guided surgery allowed the resection of additional nodules, enhancing the total tumor burden resection by 9.8 ± 0.7%, 8.5 ± 0.8%, and 3.9 ± 1.2% with Angiostamp800, Bevacizumab-IRDye 800CW and ICG, respectively. Interestingly, among the resected nodules, 15% were false-positive with ICG, compared to only 1.4% with Angiostamp800 and 3.5% with Bevacizumab-IRDye 800CW. Furthermore, conventional surgery removed only 69.0 ± 3.9% of the total tumor burden after neoadjuvant chemotherapy. Fluorescence-guided surgery with Angiostamp800 and Bevacizumab-IRDye 800CW increased the total tumor burden resection to 88.7 ± 4.3%, whereas ICG did not improve surgery at all. Bevacizumab-IRDye 800CW and Angiostamp800 better detect ovarian tumors and metastases than the clinically used fluorescent tracer ICG, and can help surgeons completely remove tumors, especially after surgery neoadjuvant chemotherapy.

Amphiregulin promotes BAX inhibition and resistance to gefitinib in non-small-cell lung cancers.

Molecular resistance mechanisms affecting the efficiency of receptor tyrosine kinase inhibitors such as gefitinib in non-small-cell lung cancer (NSCLC) cells are not fully understood. Amphiregulin (Areg) overexpression has been proposed to predict NSCLC resistance to gefitinib and we have established that Areg-overexpressing H358 NSCLC cells resist apoptosis. Here, we demonstrate that Areg prevents gefitinib-induced apoptosis in NSCLC cells. We show that H358 cells are resistant to gefitinib in contrast to H322 cells, which do not overexpress Areg. Inhibition of Areg expression by small-interfering RNAs (siRNAs) restores gefitinib sensitivity in H358 cells, whereas addition of recombinant Areg confers resistance in H322 cells. Areg knockdown overcomes resistance to gefitinib and induced apoptosis in NSCLC H358 cells in vitro and in vivo. Under gefitinib treatment, Areg decreases the expression of the proapoptotic protein BAX, inhibits its conformational change and its mitochondrial translocation. Thus, in the presence of Areg, gefitinib-mediated apoptosis is reduced because BAX is sequestered in the cytoplasm. This suggests that treatments using epidermal growth factor receptor (EGFR) inhibitors may be poorly efficient in patients with elevated levels of Areg. These findings indicate the need for inhibition of Areg to enhance the efficiency of the EGFR inhibitors in patients suffering NSCLC.

Amphiregulin promotes resistance to gefitinib in nonsmall cell lung cancer cells by regulating Ku70 acetylation.

Multiple molecular resistance mechanisms reduce the efficiency of receptor tyrosine kinase inhibitors such as gefitinib in non-small cell lung cancer (NSCLC). We previously demonstrated that amphiregulin (Areg) inhibits gefitinib-induced apoptosis in NSCLC cells by inactivating the proapoptotic protein BAX. In this part of the investigation, we studied the molecular mechanisms leading to BAX inactivation. We show that Areg prevents gefitinib-mediated acetylation of Ku70. This augments the BAX-Ku70 interaction and therefore prevents BAX-mediated apoptosis. Accordingly, Areg or Ku70 knock down restore BAX activation and apoptosis in gefitinib-treated H358 cells in vitro. In addition, overexpression of the histone acetyltransferase (HAT) CREB-binding protein (CBP) or treatments with histone deacetylase (HDAC) inhibitors sensitize H358 cells to gefitinib. Moreover, a treatment with vorinostat, a HDAC inhibitor strongly sensitized tumors to gefitinib in vivo. These findings suggest new prospects in combining both HDAC and epidermal growth factor receptor inhibitors for the treatment of NSCLC.

Clustering and internalization of integrin alphavbeta3 with a tetrameric RGD-synthetic peptide.

Integrin alpha(v)beta(3) is overexpressed on neoendothelial cells and frequently on tumor cells. We have developed a peptide-like scaffold (regioselectively addressable functionalized template, RAFT), which holds four cyclo(-RGDfK-) (cRGD) motifs and proved that this molecule (called regioselectively addressable functionalized template-arginine-glycine-aspartic acid, RAFT-RGD) targets integrin alpha(v)beta(3) in vitro and in vivo. Using fluorescence correlation spectroscopy (FCS), we measured the constant of affinity (K(D)) of the RAFT-RGD for purified integrins. K(D) values rose from 3.87 nmol/l for RAFT-RGD to 41.70 nmol/l for cyclo(-RGDfK-). In addition, RAFT-RGD inhibited alpha(v)beta(3) lateral mobility in the cell membrane, probably due to the formation of integrin clusters as demonstrated by fluorescence recovery after photobleaching (FRAP). This was confirmed by electronic microscopy data, which established the formation of molecular complexes containing two integrins in the presence of RAFT-RGD but not cRGD or regioselectively addressable functionalized template-arginine-alanine- aspartic acid (RAFT-RAD). Using an enzyme-linked immunosorbent assay (ELISA), we proved that 1 micromol/l RAFT-RGD increased by 79% alpha(v)beta(3) internalization via clathrin-coated vesicles. Conversely, cRGD was internalized without modifying alpha(v)beta(3) internalization. Although RGD has been known for >20 years, this is the first study to formerly establish the relationships among multimeric presentation, increased affinity, and subsequent integrin-mediated cointernalization. These results strongly support the rationale for using multimeric RGD-peptides as targeting vectors for imaging, diagnosis, or therapy of cancers.

Photodynamic Diagnosis and Therapy for Peritoneal Carcinomatosis: Emerging Perspectives.

Peritoneal carcinomatosis occurs frequently in patients with advanced stage gastrointestinal and gynecological cancers. The wide-spread peritoneal micrometastases indicate a poor outlook, as the tumors are difficult to diagnose and challenging to completely eradicate with cytoreductive surgery and chemotherapeutics. Photodynamic diagnosis (PDD) and therapy (PDT), modalities that use photosensitizers for fluorescence detection or photochemical treatment of cancer, are promising theranostic approaches for peritoneal carcinomatosis. This review discusses the leading clinical trials, identifies the major challenges, and presents potential solutions to advance the use of PDD and PDT for the treatment of peritoneal carcinomatosis. While PDD for fluorescence-guided surgery is practically feasible and has achieved clinical success, large randomized trials are required to better evaluate the survival benefits. Although PDT is feasible and combines well with clinically used chemotherapeutics, poor tumor specificity has been associated with severe morbidity. The major challenges for both modalities are to increase the tumor specificity of the photosensitizers, to efficiently treat peritoneal microtumors regardless of their phenotypes, and to improve the ability of the excitation light to reach the cancer tissues. Substantial progress has been achieved in (1) the development of targeted photosensitizers and nanocarriers to improve tumor selectivity, (2) the design of biomodulation strategies to reduce treatment heterogeneity, and (3) the development of novel light application strategies. The use of X-ray-activated PDT during whole abdomen radiotherapy may also be considered to overcome the limited tissue penetration of light. Integrated approaches that take advantage of PDD, cytoreductive surgery, chemotherapies, PDT, and potentially radiotherapy, are likely to achieve the most effective improvement in the management of peritoneal carcinomatosis.

Stapled peptide targeting the CDK4/Cyclin D interface combined with Abemaciclib inhibits KRAS mutant lung cancer growth.

CDK4/cyclin D kinase constitutes an attractive pharmacological target for development of anticancer therapeutics, in particular in KRAS-mutant lung cancer patients, who have a poor prognosis and no targeted therapy available yet. Although several ATP-competitive inhibitors of CDK4 have been developed for anticancer therapeutics, they suffer from limited specificity and efficacy. Methods: As an alternative to ATP-competitive inhibitors we have designed a stapled peptide to target the main interface between CDK4 and cyclin D, and have characterized its physico-chemical properties and affinity to bind cyclin D1. Results: We have validated a positive correlation between CDK4/cyclin D level and KRAS mutation in lung cancer patients. The stapled peptide enters cells rapidly and efficiently, and inhibits CDK4 kinase activity and proliferation in lung cancer cells. Its intrapulmonary administration in mice enables its retention in orthotopic lung tumours and complete inhibition of their growth when co-administered with Abemaciclib. Conclusion: The stapled peptide targeting the main interface between CDK4 and cyclin D provides promising therapeutic perspectives for patients with lung cancer.

A large scale proteome analysis of the gefitinib primary resistance overcome by KDAC inhibition in KRAS mutated adenocarcinoma cells overexpressing amphiregulin.

KDAC inhibitors (KDACi) overcome gefitinib primary resistance in non-small cell lung cancer (NSCLC) including mutant-KRAS lung adenocarcinoma. To identify which proteins are involved in the restoration of this sensitivity and to provide new therapeutic targets for mutant-KRAS lung adenocarcinoma, we performed an iTRAQ quantitative proteomic analysis after subcellular fractionation of H358-NSCLC treated with gefitinib and KDACi (TSA/NAM) versus gefitinib alone. The 86 proteins found to have been significantly dysregulated between the two conditions, were mainly involved in cellular metabolism and cell transcription processes. As expected, the pathway related to histone modifications was affected by the KDACi. Pathways known for controlling tumor development and (chemo)-resistance (miRNA biogenesis/glutathione metabolism) were affected by the KDACi/gefitinib treatment. Moreover, 57 dysregulated proteins were upstream of apoptosis (such as eEF1A2 and STAT1) and hence provide potential therapeutic targets. The inhibition by siRNA of eEF1A2 expression resulted in a slight decrease in H358-NSCLC viability. In addition, eEF1A2 and STAT1 siRNA transfections suggested that both STAT1 and eEF1A2 prevent AKT phosphorylation known for enhancing gefitinib resistance in NSCLC. Therefore, altogether our data provide new insights into proteome regulations in the context of overcoming the NSCLC resistance to gefitinib through KDACi in H358 KRAS mutated and amphiregulin-overexpressing NSCLC cells.

The pyrrolopyrimidine colchicine-binding site agent PP-13 reduces the metastatic dissemination of invasive cancer cells in vitro and in vivo.

Standard chemotherapies that interfere with microtubule dynamics are a chemotherapeutic option used for the patients with advanced malignancies that invariably relapse after targeted therapies. However, major efforts are needed to reduce their toxicity, optimize their efficacy, and reduce cancer chemoresistance to these agents. We previously identified a pyrrolo[2,3d]pyrimidine-based microtubule-depolymerizing agent (PP-13) that binds to the colchicine site of ß-tubulin and exhibits anticancer properties in solid human cancer cells, including chemoresistant subtypes. Here, we investigated the therapeutic potential of PP-13 in vitro and in vivo. PP-13 induced a mitotic blockade and apoptosis in several cancer cells cultured in two-dimensions or three-dimensions spheroids, in conjunction with reduced cell proliferation. Capillary-like tube formation assays using HUVECs showed that PP-13 displayed antiangiogenic properties. It also inhibited cancer cell motility and invasion, in in vitro wound-healing and transwell migration assays. Low concentration PP-13 (130 nmol.L-1) treatment significantly reduced the metastatic invasiveness of human cancer cells engrafts on chicken chorioallantoic membrane. In nude mice, 0.5 or 1 mg.kg-1 PP-13 intraperitoneally administered three-times a week reduced the sizes of paclitaxel-refractory orthotopic breast tumors, delayed the progression of metastasis, and decreased the global metastatic load compared to 0.5 mg.kg-1 paclitaxel or vehicle alone. PP-13 did not show any apparent early adverse effect in vivo. These data suggest that PP-13 is a promising alternative to standard chemotherapy in antimitotic drug-refractory tumors, especially through its impact on metastasis.

Anti-tumor efficacy of hyaluronan-based nanoparticles for the co-delivery of drugs in lung cancer.

Combinations of therapeutic agents could synergistically enhance the response of lung cancer cells. Co-delivery systems capable of transporting chemotherapeutics with different physicochemical properties and with the simultaneous release of drugs remain elusive. Here, we assess the ability of nanoparticles of 30-nm diameter obtained from the self-assembly of hyaluronan-based copolymer targeting CD44 receptors to encapsulate both gefitinib and vorinostat for effective combinational lung cancer treatment. Drug loading was performed by nanoprecipitation. Drug release experiments showed a slow release of both drugs after 5 days. Using two- and three-dimensional lung adenocarcinoma cell cultures, we observed that the nanoparticles were mostly found at the periphery of the CD44-expressing spheroids. These drug-loaded nanoparticles were as cytotoxic as free drugs in the two- and three-dimensional systems and toxicity was due to apoptosis induction. In mouse models, intravenous injection of hyaluronan-based nanoparticles showed a selective delivery to subcutaneous CD44-overexpressing tumors, despite a significant liver capture. In addition, the systemic toxicity of the free drugs was reduced by their co-delivery using the nanoparticles. Finally, intrapulmonary administration of drug-loaded nanoparticles, to avoid a possible hepatic toxicity due to their accumulation in the liver, showed a stronger inhibition of orthotopic lung tumor growth compared to free drugs. In conclusion, hyaluronan-based nanoparticles provide active targeting partially mediated by CD44, less-toxic drug release and improved antitumor efficiency.

Nuclear translocation of IGF1R by intracellular amphiregulin contributes to the resistance of lung tumour cells to EGFR-TKI.

Many Receptor Tyrosine Kinases translocate from the cell surface to the nucleus in normal and pathological conditions, including cancer. Here we report the nuclear expression of insulin-like growth factor-1 receptor (IGF1R) in primary human lung tumours. Using lung cancer cell lines and lung tumour xenografts, we demonstrate that the epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) gefitinib induces the nuclear accumulation of IGF1R in mucinous lung adenocarcinoma by a mechanism involving the intracellular re-localization of the growth factor amphiregulin. Amphiregulin allows the binding of IGF1R to importin-ß1 and promotes its nuclear transport. The nuclear accumulation of IGF1R by amphiregulin induces cell cycle arrest through p21WAF1/CIP1 upregulation, and prevents the induction of apoptosis in response to gefitinib. These results identify amphiregulin as the first nuclear localization signal-containing protein that interacts with IGF1R and allows its nuclear translocation. Furthermore they indicate that nuclear expression of IGF1R contributes to EGFR-TKI resistance in lung cancer.

Plasma Circulating Tumor DNA Levels for the Monitoring of Melanoma Patients: Landscape of Available Technologies and Clinical Applications.

Melanoma is a cutaneous cancer with an increasing worldwide prevalence and high mortality due to unresectable or metastatic stages. Mutations in BRAF, NRAS, or KIT are present in more than 60% of melanoma cases, but a useful blood-based biomarker for the clinical monitoring of melanoma patients is still lacking. Thus, the analysis of circulating tumor cells (CTCs) and/or cell-free circulating tumor DNA (ctDNA) analysis from blood (liquid biopsies) appears to be a promising noninvasive, repeatable, and systemic sampling tool for detecting and monitoring melanoma. Here, we review the molecular biology-based strategies used for ctDNA quantification in melanoma patients, as well as their main clinical applications. Droplet digital PCR (ddPCR) and next generation sequencing (NGS) technologies appear to be two versatile and complementary strategies to study rare variant mutations for the detection and monitoring of melanoma progression. Among the different clinical uses of ctDNA, we highlight the assessment of molecular heterogeneity and the identification of genetic determinants for targeted therapy as well as the analysis of acquired resistance. Importantly, ctDNA quantification might also be a novel biomarker with a prognostic value for melanoma patients.

Identification of pyrrolopyrimidine derivative PP-13 as a novel microtubule-destabilizing agent with promising anticancer properties.

Despite the emergence of targeted therapies and immunotherapy, chemotherapy remains the gold-standard for the treatment of most patients with solid malignancies. Spindle poisons that interfere with microtubule dynamics are commonly used in chemotherapy drug combinations. However, their troublesome side effects and the emergence of chemoresistance highlight the need for identifying alternative agents. We performed a high throughput cell-based screening and selected a pyrrolopyrimidine molecule (named PP-13). In the present study, we evaluated its anticancer properties in vitro and in vivo. We showed that PP-13 exerted cytotoxic effects on various cancer cells, including those resistant to current targeted therapies and chemotherapies. PP-13 induced a transient mitotic blockade by interfering with both mitotic spindle organization and microtubule dynamics and finally led to mitotic slippage, aneuploidy and direct apoptotic death. PP-13 was identified as a microtubule-targeting agent that binds directly to the colchicine site in ß-tubulin. Interestingly, PP-13 overcame the multidrug-resistant cancer cell phenotype and significantly reduced tumour growth and metastatic invasiveness without any noticeable toxicity for the chicken embryo in vivo. Overall, PP-13 appears to be a novel synthetic microtubule inhibitor with interesting anticancer properties and could be further investigated as a potent alternative for the management of malignancies including chemoresistant ones.