Additional chemotherapy for EGFRm patients with the continued presence of plasma ctDNA EGFRm at week 3 after start of osimertinib first-line treatment (PACE)

TPS9157

Background: Epidermal growth factor receptor (EGFR) – mutated non-small cell lung cancer (NSCLC) is susceptible to EGFR targeting tyrosine kinase inhibitors (TKI), such as the third generation TKI osimertinib. However, response rate and duration vary between patients. Among others, the specific subtype of EGFR-mutation, its co-occurrence with other genetic alterations, and the detection of phosphorylated EGFR (pEGFR) in the plasma, and its clearance upon treatment were previously identified as markers that predict therapy response. A high proportion of patients with early (3-6 weeks after start) pEGFR clearance from plasma show impressive survival upon single-agent TKI. However, failure to achieve early clearance upon Osimertinib is associated with unfavorable outcome. For these patients, treatment concepts are lacking. Here, we report about the initiation of a clinical trial that evaluates the combination of EGFR-directed TKI and platinum-based chemotherapy as an early treatment escalation strategy for this high-risk patient population. Methods: PACE is a prospective multicenter single-arm investigator-initiated phase II trial. Patients with NSCLC harboring L858R or del19 EGFR mutation, who are treated with first-line Osimertinib are subjected to liquid biopsy-based early response assessment three weeks after start of therapy. Failure to clear pEGFR from plasma at this time point triggers treatment escalation with the addition of platinum-based doublet chemotherapy to the Osimertinib treatment. The primary outcome measure of the trial is progression-free survival (PFS), with the objective to assess the efficacy of biomarker-driven escalation of osimertinib therapy with a combination platinum-based regimen. Secondary outcome measures are the overall response rate (ORR), overall survival (OS), and the Quality of life (QLQ-C30, CTCAE-PROs) of the treated patients. In exploratory analyses, we will assess whether specific patterns of co-mutations are associated with early treatment failure (upon TKI) and pEGFR persistence. Fig. 1 illustrates the trial concept. A sample of 46 subjects achieves 80% power at a 0.05 significance level to detect a PFS of 14.4 months in the experimental treatment group when the PFS of the historic control group is 9.1 months; a total of 400 patients need to be screened within the national Network Genomic Medicine. Enrollment started in 12/2021. The clinical trial is supported by AstraZeneca and Guardant. EudraCT registration number: 2019-004757-88 .

Adaptor protein Lnk binds to PDGF receptor and inhibits PDGF-dependent signaling

OBJECTIVE

Platelet-derived growth factor receptors α and β (PDGFRA, PDGFRB) are frequently expressed on hematopoietic cells and regulate cellular responses such as proliferation, differentiation, survival, and transformation. Stimulation by autocrine loops or activation by chromosomal translocation makes them important factors in development of hematopoietic disorders. Interaction with the ligand PDGF results in activation of the tyrosine kinase domain and phosphorylation of tyrosine residues, thereby creating binding sites for molecules containing Src homology 2 domains. We hypothesized that one such protein may be Lnk, a negative regulator of cytokine receptors, including Mpl, EpoR, c-Kit, and c-Fms.

MATERIALS AND METHODS

Interaction of Lnk with PDGFRA, PDGFRB, or leukemogenic FIP1L1-PDGFRA or TEL-PDGFRB was studied in cotransfected 293T cells. Effects of Lnk on PDGFR signaling were shown in 293T and NIH3T3 cells, whereas its influence on either PDGF-dependent or factor-independent growth was investigated using Ba/F3 or 32D cells expressing wild-type PDGFR, FIP1L1-PDGFRA, or TEL-PDGFRB.

RESULTS

We show that Lnk binds to PDGFR after exposure of cells to PDGF. Furthermore, Lnk can bind the FIP1L1-PDGFRA fusion protein. Mutation or deletion of the Lnk Src homology 2 domain completely abolished binding of Lnk to FIP1L1-PDGFRA, but just partly prevented binding to PDGFRA or PDGFRB. Expression of Lnk inhibited proliferation of PDGF-dependent Ba/F3 cells and diminished phosphorylation of Erk in PDGF-treated NIH3T3. 32D cells transformed by either FIP1L1-PDGFRA or TEL-PDGFRB stopped growing when Lnk was expressed.

CONCLUSIONS

Lnk is a negative regulator of PDGFR signaling. Development of Lnk mimetic drugs might provide a novel therapeutic strategy for myeloproliferative disorders.

Activation of Wnt signalling in acute myeloid leukemia by induction of Frizzled-4

Wnt signalling regulates proliferation, self renewal and cell fate. Aberrant Wnt signalling is thought to contribute to AML pathogenesis by enhancing self renewal. Herein, we provide evidence for increased expression of Frizzled-4, a receptor for Wnt ligands, in primary AML blasts compared to normal bone marrow on the protein level. In addition, Frizzled-4 is highly expressed in human CD34 positive cells as well as in lineage negative sorted mouse bone marrow cells. Functionally, Frizzled-4 expression modulates apoptosis and enhances Wnt3a induced beta-catenin stability in myeloid progenitor cells. Frizzled-4-dependent beta-catenin stabilization is dkk-1 sensitive, implicating a specific Wnt-ligand/Frizzled-receptor interaction. These findings indicate enhanced sensitivity of AML blasts for Wnt-ligands and suggest an additional mechanism of Wnt signalling activation in the pathogenesis of AML.

Activation of Wnt signaling in cKit-ITD mediated transformation and imatinib sensitivity in acute myeloid leukemia

The Wnt-signaling pathway plays a critical role in directing cell fate during embryogenesis and also in the pathogenesis of cancer. In leukemia, it is well described that activating internal tandem duplications (ITD) mutations in receptor tyrosine kinases like cKit or Flt3 confer to the pathogenesis of cancer. Here, we analyzed whether Wnt-signaling plays a role in cKit-ITD mediated transformation. Stably transfected 32D cells with cKit-ITD cells had higher beta-Catenin protein levels compared to the cKit-WT. Analysis of beta-Catenin mRNA and protein levels revealed that beta-Catenin was regulated at post-transcriptional level in cKit-ITD as well as Flt3-ITD compared to the wildtype. Signaling analyses revealed higher-phosphorylation of GSK3beta by oncogenic cKit-ITD. Moreover, activation of Wnt signaling was confirmed by constitutive activation of c-myc luciferase by cKit-ITD cells. Importantly, using dominant negative TCF4, we show that activation of Wnt signaling plays an important role in cKit mediated transformation of myeloid cells. Application of specific receptor tyrosine kinase inhibitors for Flt3 or cKit result in a decrease of beta-Catenin that underwent with a decrease of GSK3beta phosphorylation, suggesting an indirect mechanism of beta-Catenin regulation by oncogenic receptor tyrosine kinases in both ITD mutations. Our study shows the importance of activation of Wnt signaling in leukemia and suggests as attractive target for future therapeutical approaches.

Wnt signaling regulates transendothelial migration of monocytes

The Wnt-signaling pathway plays a critical role in directing cell fate during embryogenesis. Several lines of evidence also suggest a role in inflammatory processes. Here, we analyzed whether Wnt signaling plays a role in leukocyte inflammatory responses. Monocytes from healthy donors expressed different Frizzled receptors, which are ligands for the Wnt molecules. Activation of the Wnt/beta-catenin pathway by LiCl or Wnt3a increased beta-catenin protein levels in monocytes but not in granulocytes. It is interesting that the activation of Wnt/beta-catenin signaling via Wnt3a in monocytes resulted in a decrease in migration through an endothelial layer (human dermal microvascular endothelial cell-1). Further experiments revealed that the decrease in transendothelial migration was associated with specific monocyte adherence to endothelial cells after Wnt exposure. The specificity was verified by a lack of Wnt3a-induced adhesion to fibronectin, laminin, or collagen compared with endothelial interaction. Analysis of the distribution of beta-catenin revealed a Wnt3a-induced increase of beta-catenin in the cytoplasm. Wnt3a exposure did not result in any activation of the classical Wnt-target gene c-myc or a Wnt-target gene involved in cell adhesion (Connexin43). Our study implicates for the first time a role of canonical Wnt signaling in inflammatory processes in monocytes.

The evolution of a chairside CAD/CAM system for dental restorations

Since its introduction more than 15 years ago, the CEREC method for the chairside fabrication of all-ceramic restorations has steadily earned a loyal following among dentists. The rapid creation of tooth-colored restorations, including full-coverage crowns, at chairside has been achieved through quick and easy optical impression-taking, simple designing, and precise machining. This article describes the evolution of this technology's development and its incorporation into the dental practice.