Jonathan Clarhaut

Semaphorin SEMA3F Affects Multiple Signaling Pathways in Lung Cancer Cells

Loss of SEMA3F occurs frequently in lung cancer and correlates with advanced stage of disease. We previously reported that SEMA3F blocked tumor formation by H157 lung cancer cells in a rat orthotopic model. This was associated with loss of activated alpha(V)beta(3) integrin, impaired cell adhesion to extracellular matrix components, and down-regulation of phospho-extracellular signal-regulated kinase 1/2 (ERK1/2). These results suggested that SEMA3F might interfere with integrin outside-in signaling. In the present report, we found that SEMA3F decreased adhesion to vitronectin, whereas integrin-linked kinase (ILK) kinase activity was down-regulated in SEMA3F-expressing H157 cells. Exposure to SEMA3F-conditioned medium led to diminution of phospho-ERK1/2 in four of eight lung cancer cell lines, and ILK silencing by small interfering RNA led to similar loss of phospho-ERK1/2 in H157 cells. Moreover, SEMA3F expression (with constitutive and inducible systems) also reduced AKT and signal transducer and activator of transcription 3 (STAT3) phosphorylation independently of ILK-ERK1/2. These signaling changes extended downstream to hypoxia-inducible factor-1alpha (HIF-1alpha) protein and vascular endothelial growth factor (VEGF) mRNA levels, which were both reduced in three of four SEMA3F-transfected cell lines. Mechanistically, the effects on HIF-1alpha were consistent with inhibition of its AKT-driven protein translation initiation, with no effect on HIF-1alpha mRNA level or protein degradation. Furthermore, when H157 cells were injected s.c. in nude mice, tumors derived from SEMA3F-expressing cells showed lower microvessel density and tumor growth. These results show that SEMA3F negatively affects ILK-ERK1/2 and AKT-STAT3 signaling, along with inhibition of HIF-1alpha and VEGF. These changes would be anticipated to contribute significantly to the observed antitumor activity of SEMA3F.

The First Generation of β-Galactosidase-Responsive Prodrugs Designed for the Selective Treatment of Solid Tumors in Prodrug Monotherapy†

Massive attack: Galactoside prodrugs have been designed that can be selectively activated by lysosomal β-galactosidase located inside cancer cells expressing a specific tumor-associated receptor. This efficient enzymatic process triggers a potent cytotoxic effect, releasing the potent antimitotic agent MMAE and allowing the destruction of both receptor-positive and surrounding receptor-negative tumor cells.

β-Glucuronidase-responsive prodrugs for selective cancer chemotherapy: an update.

The design of novel antitumor agents allowing the destruction of malignant cells while sparing healthy tissues is one of the major challenges in medicinal chemistry. In this context, the use of non-toxic prodrugs programmed to be selectively activated by beta-glucuronidase present at high concentration in the microenvironment of most solid tumors has attracted considerable attention. This review summarizes the major progresses that have been realized in this field over the past ten years. This includes the new prodrugs that have been designed to target a wide variety of anticancer drugs, the prodrugs employed in the course of a combined therapy, the dendritic glucuronide prodrugs and the concept of β-glucuronidase-responsive albumin binding prodrugs.

Serotonin and cancer: what is the link?

Serotonin (5-hydroxytryptamine, 5-HT) is a biogenic monoamine that acts as a neurotransmitter in the central nervous system, local mediator in the gut and vasoactive agent in the blood. Serotonin exerts its multiple, sometimes opposing actions through interaction with a multiplicity of receptors coupled to various signalling pathways. In addition to its well-known functions, serotonin has been shown to be a mitogenic factor for a wide range of normal and tumoral cells. Serotonin exhibits a growth stimulatory effect in aggressive cancers and carcinoids more often through 5- HT1 and 5-HT2 receptors. In contrast, low doses of serotonin can inhibit tumour growth via the decrease of blood supply to the tumour, suggesting that the role of serotonin on tumour growth is concentration-dependent. Data are also available on serotonin involvement in cancer cell migration, metastatic processes and as a mediator of angiogenesis. Moreover, the progression of some tumours is accompanied by a dysregulation of the pattern of serotonin receptor expressions. Serum serotonin level was found to be suitable for prognosis evaluation of urothelial carcinoma in the urinary bladder, adenocarcinoma of the prostate and renal cell carcinoma. In some cases, antagonists of serotonin receptors, inhibitors of selective serotonin transporter and of serotonin synthesis have been successfully used to prevent cancer cell growth. This review revaluates serotonin involvement in several types of cancer and at different stages of their progression.

Synthesis and Antitumor Efficacy of a β-Glucuronidase-Responsive Albumin-Binding Prodrug of Doxorubicin

In this paper we describe the synthesis and biological evaluation of the first β-glucuronidase-responsive albumin-binding prodrug designed for the selective delivery of doxorubicin at the tumor site. This prodrug leads to superior antitumor efficacy in mice compared to HMR 1826, a well-known glucuronide prodrug of doxorubicin that cannot bind covalently to circulating albumin. Furthermore, this compound inhibits tumor growth in a manner similar to that of doxorubicin while avoiding side effects induced by the free drug.

Synthesis and modeling of new benzofuranone histone deacetylase inhibitors that stimulate tumor suppressor gene expression.

New benzofuranones were synthesized and evaluated toward NCI-H661 non-small cell lung cancer cells. Benzamide derivatives possessed micromolar antiproliferative and histone deacetylase inhibitory activities and modulate histone H4 acetylation. Hydroxamic acids were found to be potent nanomolar antiproliferative agents and HDAC inhibitors. Computational analysis presented a rationale for the activities of the hydroxamate derivatives. Impact of the HDAC inhibition on the expression of E-cadherin and the SEMA3F tumor suppressor genes revealed new promising compounds for lung cancer treatments.

A self-immolative dendritic glucuronide prodrug of doxorubicin

The first self-immolative dendritic glucuronide prodrug of doxorubicin was studied with the aim to target β-glucuronidase overexpressed in the microenvironment of numerous tumors. This compound includes a chemical amplifier programmed to release two molecules of doxorubicin after a single enzymatic activation step. Upon β-glucuronidase activation, the dendritic prodrug was twice more toxic than its monomeric counterpart against H661 lung cancer cells.

The gap junction protein Cx43 is involved in the bone-targeted metastatic behaviour of human prostate cancer cells.

For decades, cancer was associated with gap-junction defects. However, more recently it appeared that the gap junction proteins (connexins) could be re-expressed and participate to cancer cell dissemination during the late stages of tumor progression. Since primary tumors of prostate cancer (PCa) are known to be connexin deficient, it was interesting to verify whether their bone-targeted metastatic behaviour could be influenced by the re-expression of the connexin type (connexin43) which is originally present in prostate tissue and highly expressed in bone where it participates to the differentiation of osteoblastic cells. Thus, we investigated the effect of the increased Cx43 expression, by retroviral infection, on the metastatic behaviour of two well-characterized cell lines (PC-3 and LNCaP) representing different stages of PCa progression. It appeared that Cx43 differently behaved in those cell lines and induced different phenotypes. In LNCaP, Cx43 was functional, localized at the plasma membrane and its high expression was correlated with a more aggressive phenotype both in vitro and in vivo. In particular, those Cx43-expressing LNCaP cells exhibited a high incidence of osteolytic metastases generated by bone xenografts in mice. Interestingly, LNCaP cells were also able to decrease the proliferation of cocultured osteoblastic cells. In contrast, the increased expression of Cx43 in PC-3 cells led to an unfunctional, cytoplasmic localization of the protein and was correlated with a reduction of proliferation, adhesion and invasion of the cells. In conclusion, the localization and the functionality of Cx43 may govern the ability of PCa cells to metastasize in bones.

Synthesis and biological evaluation of glucuronide prodrugs of the histone deacetylase inhibitor CI-994 for application in selective cancer chemotherapy

Two glucuronide prodrugs of the histone deacetylase inhibitor CI-994 were synthesized. These compounds were found to be soluble in aqueous media and stable under physiological conditions. The carbamoyl derivatisation of CI-994 significantly decreased its toxicity towards NCI-H661 lung cancer cells. Prodrug incubation with beta-glucuronidase in the culture media led efficiently to the release of the parent drug and thereby restoring its ability to decrease cell proliferation, to inhibit HDAC and to induce E-Cadherin expression.

Down-regulation of connexin43 expression reveals the involvement of caveolin-1 containing lipid rafts in human U251 glioblastoma cell invasion

Glioblastoma cells are characterized by high proliferation and invasive capacities. Tumor development has been associated with a decrease of gap‐junctional intercellular communication, but the concrete involvement of gap junction proteins, connexins, remains elusive since they are also suspected to promote cell invasion. In order to better understand how connexins control the glioma cell phenotype, we studied the consequences of inhibiting the intrinsic expression of the major astrocytic connexin, Connexin43, in human U251 glioblastoma cells by the shRNA strategy. The induced down‐regulation of Cx43 expression has various effects on the U251 cells such as increased clonogenicity, angiogenesis and decreased adhesion on specific extracellular matrix proteins. We demonstrate that the invasion capacity measured in vitro and ex vivo correlates with Cx43 expression level. For the first time in a cancer cell context, our work demonstrates that Cx43 cofractionates, colocalizes and coimmunoprecipitates with a lipid raft marker, caveolin‐1 and that this interaction is inversely correlated to the level of Cx43. This localization of Cx43 in these lipid raft microdomains regulates both homo‐ and heterocellular gap junctional communications (respectively between U251 cells, or between U251 cells and astrocytes). Moreover, the adhesive and invasive capacities are not dependent, in our model, on Cav‐1 expression level. Our results tend to show that heterocellular gap junctional communication between cancer and stroma cells may affect the behavior of the tumor cells. Altogether, our data demonstrate that Cx43 controls the tumor phenotype of glioblastoma U251 cells and in particular, invasion capacity, through its localization in lipid rafts containing Cav‐1.