Targeted activity of the small molecule kinase inhibitor Pz-1 towards RET and TRK kinases

Discovery of 9H-pyrimido[4,5-b]indole derivatives as dual RET/TRKA inhibitors

Aberrant RET kinase signaling is activated in numerous cancers including lung, thyroid, breast, pancreatic, and prostate. Recent approvals of selective RET inhibitors, pralsetinib and selpercatinib, has shifted the focus of RET kinase drug discovery programs towards the development of selective inhibitors. However, selective inhibitors invariably lose efficacy as the selective nature of the inhibitor places Darwinian-like pressure on the tumor to bypass treatment through the selection of novel oncogenic drivers. Further, selective inhibitors are restricted for use in tumors with specific genetic backgrounds that do not encompass diverse patient classes. Here we report the identification of a pyrimido indole RET inhibitor found to also have activity against TRK. This selective dual RET/TRK inhibitor can be utilized in tumors with both RET and TRK genetic backgrounds and can also provide blockade of NTRK-fusions that are selected for from RET inhibitor treatments. Efforts towards developing dual RET/TRK inhibitors can be beneficial in terms of encompassing more diverse patient classes while also achieving blockade against emerging resistance mechanisms.

Design and Synthesis of Novel Thieno[3,2-c]quinoline Compounds with Antiproliferative Activity on RET-Dependent Medullary Thyroid Cancer Cells

RET kinase gain-of-function mutations represent the main cause of the high aggressiveness and invasiveness of medullary thyroid cancer (MTC). The selective inhibition of the RET kinase is a suitable strategy for the treatment of this endocrine neoplasia. Herein, we performed an innovative ligand-based virtual screening protocol using the DRUDITonline web service, focusing on the RET kinase as a biological target. In this process, thieno[3,2-c]quinolines 6a-e and 7a-e were proposed as new potential RET inhibitors. The selected compounds were synthetized by appropriate synthetic strategies, and in vitro evaluation of antiproliferative properties conducted on the particularly aggressive MTC cell line TT(C634R) identified compounds 6a-d as promising anticancer agents, with IC50 values in the micromolar range. Further structure-based computational studies revealed a significant capability of the most active compounds to the complex RET tyrosine kinase domain. The interesting antiproliferative results supported by in silico predictions suggest that these compounds may represent a starting point for the development of a new series of small heterocyclic molecules for the treatment of MTC.

RET signaling in breast cancer therapeutic resistance and metastasis

RET, a single-pass receptor tyrosine kinase encoded on human chromosome 10, is well known to the field of developmental biology for its role in the ontogenesis of the central and enteric nervous systems and the kidney. In adults, RET alterations have been characterized as drivers of non-small cell lung cancer and multiple neuroendocrine neoplasms. In breast cancer, RET signaling networks have been shown to influence diverse functions including tumor development, metastasis, and therapeutic resistance. While RET is known to drive the development and progression of multiple solid tumors, therapeutic agents selectively targeting RET are relatively new, though multiple multi-kinase inhibitors have shown promise as RET inhibitors in the past; further, RET has been historically neglected as a potential therapeutic co-target in endocrine-refractory breast cancers despite mounting evidence for a key pathologic role and repeated description of a bi-directional relationship with the estrogen receptor, the principal driver of most breast tumors. Additionally, the recent discovery of RET enrichment in breast cancer brain metastases suggests a role for RET inhibition specific to advanced disease. This review assesses the status of research on RET in breast cancer and evaluates the therapeutic potential of RET-selective kinase inhibitors across major breast cancer subtypes.

Pyrrolyldihydropyrazino[1,2-a]indoletrione Analogue Microtubule Inhibitor Induces Cell-Cycle Arrest and Apoptosis in Colorectal Cancer Cells

In this study, 2-benzyl-10a-(1H-pyrrol-2-yl)-2,3-dihydropyrazino[1,2-a]indole-1,4,10(10aH)-trione (DHPITO), a previously identified inhibitor against hepatocellular carcinoma cells, is shown to exert its cytotoxic effects by suppressing the proliferation and growth of CRC cells. An investigation of its molecular mechanism confirmed that the cytotoxic activity of DHPITO is mediated through the targeting of microtubules with the promotion of subsequent microtubule polymerisation. With its microtubule-stabilising ability, DHPITO also consistently arrested the cell cycle of the CRC cells at the G2/M phase by promoting the phosphorylation of histone 3 and the accumulation of EB1 at the cell equator, reduced the levels of CRC cell migration and invasion, and induced cellular apoptosis. Furthermore, the compound could suppress both tumour size and tumour weight in a CRC xenograft model without any obvious side effects. Taken together, the findings of the present study reveal the antiproliferative and antitumour mechanisms through which DHPITO exerts its activity, indicating its potential as a putative chemotherapeutic agent and lead compound with a novel structure.

Antiproliferative Evaluation of Novel 4-Imidazolidinone Derivatives as Anticancer Agent Which Triggers ROS-Dependent Apoptosis in Colorectal Cancer Cell

Colorectal cancer (CRC) is one of the most common causes of cancer-related death worldwide, and more therapies are needed to treat CRC. To discover novel CRC chemotherapeutic molecules, we used a series of previously synthesized novel imidazolidin-4-one derivatives to study their anticancer role in several cancer cell lines. Among these compounds, compound 9r exhibited the best anticancer activity in CRC cell lines HCT116 and SW620. We further investigated the anticancer molecular mechanism of compound 9r. We found that compound 9r induced mitochondrial pathway apoptosis in HCT116 and SW620 cells by inducing reactive oxygen species (ROS) production. Moreover, the elevated ROS generation activated the c-Jun N-terminal kinase (JNK) pathway, which further accelerated apoptosis. N-acetylcysteine (NAC), an antioxidant reagent, suppressed compound 9r-induced ROS production, JNK pathway activation, and apoptosis. Collectively, this research synthesized a series of imidazolidin-4-one derivatives, evaluated their anticancer activity, and explored the molecular mechanism of compound 9r-induced apoptosis in CRC cells. The present results suggest that compound 9r has a potential therapeutic role in CRC. Hence, it deserves further exploration as a lead compound for CRC treatment.