Wnt/β-Catenin Signaling Regulates CXCR4 Expression and [68Ga] Pentixafor Internalization in Neuroendocrine Tumor Cells

CXCR4: From Signaling to Clinical Applications in Neuroendocrine Neoplasms

There are several well-described molecular mechanisms that influence cell growth and are related to the development of cancer. Chemokines constitute a fundamental element that is not only involved in local growth but also affects angiogenesis, tumor spread, and metastatic disease. Among them, the C-X-C motif chemokine ligand 12 (CXCL12) and its specific receptor the chemokine C-X-C motif receptor 4 (CXCR4) have been widely studied. The overexpression in cell membranes of CXCR4 has been shown to be associated with the development of different kinds of histological malignancies, such as adenocarcinomas, epidermoid carcinomas, mesenchymal tumors, or neuroendocrine neoplasms (NENs). The molecular synapsis between CXCL12 and CXCR4 leads to the interaction of G proteins and the activation of different intracellular signaling pathways in both gastroenteropancreatic (GEP) and bronchopulmonary (BP) NENs, conferring greater capacity for locoregional aggressiveness, the epithelial-mesenchymal transition (EMT), and the appearance of metastases. Therefore, it has been hypothesized as to how to design tools that target this receptor. The aim of this review is to focus on current knowledge of the relationship between CXCR4 and NENs, with a special emphasis on diagnostic and therapeutic molecular targets.

WNT2B Deficiency Causes Enhanced Susceptibility to Colitis Due to Increased Inflammatory Cytokine Production

BACKGROUND & AIMS

Humans with WNT2B deficiency have severe intestinal disease, including significant inflammatory injury, highlighting a critical role for WNT2B. We sought to understand how WNT2B contributes to intestinal homeostasis.

METHODS

We investigated the intestinal health of Wnt2b knock out (KO) mice. We assessed the baseline histology and health of the small intestine and colon, and the impact of inflammatory challenge using dextran sodium sulfate (DSS). We also evaluated human intestinal tissue.

RESULTS

Mice with WNT2B deficiency had normal baseline histology but enhanced susceptibility to DSS colitis because of an increased early injury response. Although intestinal stem cells markers were decreased, epithelial proliferation was similar to control subjects. Wnt2b KO mice showed an enhanced inflammatory signature after DSS treatment. Wnt2b KO colon and human WNT2B-deficient organoids had increased levels of CXCR4 and IL6, and biopsy tissue from humans showed increased neutrophils.

CONCLUSIONS

WNT2B is important for regulation of inflammation in the intestine. Absence of WNT2B leads to increased expression of inflammatory cytokines and increased susceptibility to gastrointestinal inflammation, particularly in the colon.

Adhesive Hydrogel Patch-Mediated Combination Drug Therapy Induces Regenerative Wound Healing through Reconstruction of Regenerative Microenvironment

Regenerative wound healing involves the scarless wound healing as observed in fetal skin. Multiple features of regenerative wound healing have been well studied; however, the practical application of pro-regenerative materials to recapitulate the regenerative wound healing in adult skins has not yet been achieved. In this study, the authors identified that their novel pro-regenerative material, pyrogallol-functionalized hyaluronic acid (HA-PG) patches in combination with protein transduction domain-fused Dishevelled (Dvl)-binding motif (PTD-DBM), a peptide inhibiting the CXXC-type zinc finger protein 5 (CXXC5)-Dvl interaction, promoted regenerative wound healing in mice. The HA-PG patches loaded with this competitor peptide and valproic acid (VPA), a glycogen synthase kinase 3β (GSK3β) inhibitor, significantly inhibited scar formation during wound healing. The HA-PG patches with PTD-DBM and/or VPA inhibit the expression of differentiated cell markers such as α-smooth muscle actin (α-SMA) while inducing the expression of stem cell markers such as CD105 and Nestin. Moreover, Collagen III, an important factor for regenerative healing, is critically induced by the HA-PG patches with PTD-DBM and/or VPA, as also seen in VPA-treated Cxxc5-/- mouse fibroblasts. Overall, these findings suggest that the novel regeneration-promoting material can be utilized as a potential therapeutic agent to promote both wound healing and scar attenuation.

Wnt/β-catenin modulating drugs regulate somatostatin receptor expression and internalization of radiolabelled octreotide in neuroendocrine tumor cells

BACKGROUND

Differentiated neuroendocrine tumors (NETs) express somatostatin receptors (SSTRs), targets for therapy with either unlabeled or radioactively labeled somatostatin analogs (SSA). Associated with worse prognosis, dedifferentiated NET loose SSTR expression, which may be linked to deregulation of Wnt/β-catenin signaling on an intracellular level. The aim of the present study was to investigate the effect of Wnt/β-catenin signaling pathway alterations on SSTR expression and its function in NET.

METHODS

The NET cell lines BON-1 and QGP-1 were incubated with the Wnt-inhibitors 5-aza-2'-deoxycytidine (5-aza-CdR), Quercetin, or Niclosamide, or the Wnt activator lithium chloride (LiCl). Expression of SSTR1, SSTR2, and SSTR5 was determined by quantitative RT-PCR (qRT-PCR), immunocytomicroscopy and western blot. Changes in the Wnt pathway were analyzed by qRT-PCR of selected target genes and the TaqMan Array Human WNT Pathway. Receptor-associated function was determined by measuring the cellular uptake of [125I-Tyr3] octreotide.

RESULTS

The mRNAs of SSTRs 1-5 were expressed in both cell lines. Wnt inhibitors caused downregulation of Wnt target genes, while 5-aza-CdR had the highest inhibitory effect. LiCl lead to an upregulation of Wnt genes, which was more marked in QGP-1 cells. SSTR expression increased in both cell lines upon Wnt inhibition. All three Wnt inhibitors lead to a marked increase in the specific uptake of [125I-Tyr3]octreotide, with 5-aza-CdR showing the greatest effect (increase by more than 50% in BON-1 cells), while a decreased uptake of [125I-Tyr3]octreotide was seen upon activation of Wnt signaling by LiCl.

CONCLUSIONS

We demonstrate here that Wnt signaling orchestrates SSTR expression and function in a preclinical NET model. Wnt inhibition increases [125I-Tyr3]octreotide uptake offering an opportunity to enhance the efficacy of SSTR-targeted theranostic approaches.

Theranostics in Oncology-Thriving, Now More than Ever

Tracing its roots back to the 1940s, theranostics in nuclear oncology has proved successful mainly due to the beneficial effects of image-guided therapeutic concepts for patients afflicted with a variety of different cancers. The majority of these treatments are not only characterized by substantial prolongation of progression-free and overall survival, but are also generally safe, rendering theranostic agents as an attractive treatment option in various clinical scenarios in oncology. In this Special Issue Novel Theranostic Agents, nine original articles from around the globe provide further evidence on the use of the theranostic concept for neuroendocrine neoplasm (NEN), prostate cancer (PC), meningioma, and neuroblastoma. The investigated diagnostic and therapeutic radiotracers target not only established structures, such as somatostatin receptor, prostate-specific membrane antigen or norepinephrine transporter, but also recently emerging targets such as the C-X-C motif chemokine receptor 4. Moreover, the presented original articles also combine the concept of theranostics with in-depth read-out techniques such as radiomics or novel reconstruction algorithms on pretherapeutic scans, e.g., for outcome prediction. Even 80 years after its initial clinical introduction, theranostics in oncology continues to thrive, now more than ever.