RAF and MEK Inhibitors in Non-Small Cell Lung Cancer.

Lung cancer, despite recent advancements in survival rates, represents a significant global health burden. Non-small cell lung cancer (NSCLC), the most prevalent type, is driven largely by activating mutations in Kirsten rat sarcoma viral oncogene homologue (KRAS) and receptor tyrosine kinases (RTKs), and less in v-RAF murine sarcoma viral oncogene homolog B (BRAF) and mitogen-activated protein-kinase kinase (MEK), all key components of the RTK-RAS-mitogen-activated protein kinase (MAPK) pathway. Learning from melanoma, the identification of BRAFV600E substitution in NSCLC provided the rationale for the investigation of RAF and MEK inhibition as a therapeutic strategy. The regulatory approval of two RAF-MEK inhibitor combinations, dabrafenib-trametinib, in 2017, and encorafenib-binimetinib, in 2023, signifies a breakthrough for the management of BRAFV600E-mutant NSCLC patients. However, the almost universal emergence of acquired resistance limits their clinical benefit. New RAF and MEK inhibitors, with distinct biochemical characteristics, are in preclinical and clinical development. In this review, we aim to provide valuable insights into the current state of RAF and MEK inhibition in the management of NSCLC, fostering a deeper understanding of the potential impact on patient outcomes.

Runx2 and Polycystins in Bone Mechanotransduction: Challenges for Therapeutic Opportunities.

Bone mechanotransduction is a critical process during skeletal development in embryogenesis and organogenesis. At the same time, the type and level of mechanical loading regulates bone remodeling throughout the adult life. The aberrant mechanosensing of bone cells has been implicated in the development and progression of bone loss disorders, but also in the bone-specific aspect of other clinical entities, such as the tumorigenesis of solid organs. Novel treatment options have come into sight that exploit the mechanosensitivity of osteoblasts, osteocytes, and chondrocytes to achieve efficient bone regeneration. In this regard, runt-related transcription factor 2 (Runx2) has emerged as a chief skeletal-specific molecule of differentiation, which is prominent to induction by mechanical stimuli. Polycystins represent a family of mechanosensitive proteins that interact with Runx2 in mechano-induced signaling cascades and foster the regulation of alternative effectors of mechanotransuction. In the present narrative review, we employed a PubMed search to extract the literature concerning Runx2, polycystins, and their association from 2000 to March 2024. The keywords stated below were used for the article search. We discuss recent advances regarding the implication of Runx2 and polycystins in bone remodeling and regeneration and elaborate on the targeting strategies that may potentially be applied for the treatment of patients with bone loss diseases.

Malolactone strikes: K-Ras-G12D's Achilles' heel.

In a recent study in Nature Chemical Biology, Zheng et al. exploiting strain release by malolactone-based electrophiles designed a first-in-class covalent inhibitor that targets the elusive aspartate of the Kirsten rat sarcoma viral oncogene homolog (K-Ras)-G12D variant, which is highly prevalent in pancreatic cancer. The compound drastically inhibited oncogenic signaling and tumor growth in preclinical K-Ras-G12D-mutant pancreatic cancer models, expanding treatment potential beyond K-Ras-G12C-targeted therapies.

SOX17: escape route from immune destruction in early CRC.

In a recent report in Nature, Goto et al. reveal a novel immune-evasion mechanism adopted by early colorectal cancer (CRC) cells that is based on the transcription factor sex determining region Y (SRY)-box transcription factor 17 (SOX17). Leveraging colorectal adenoma and cancer models to perform comprehensive transcriptomic/chromatin analyses, this work shows that SOX17 generates immune-silent leucine-rich repeat-containing G protein-coupled receptor 5- (LGR5-) tumor cells, which suppress interferon gamma (IFNγ) signaling and promote immune escape.

Inhibition of the RAF/MEK/ERK Signaling Cascade in Pancreatic Cancer: Recent Advances and Future Perspectives.

Pancreatic cancer represents a formidable challenge in oncology, primarily due to its aggressive nature and limited therapeutic options. The prognosis of patients with pancreatic ductal adenocarcinoma (PDAC), the main form of pancreatic cancer, remains disappointingly poor with a 5-year overall survival of only 5%. Almost 95% of PDAC patients harbor Kirsten rat sarcoma virus (KRAS) oncogenic mutations. KRAS activates downstream intracellular pathways, most notably the rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling axis. Dysregulation of the RAF/MEK/ERK pathway is a crucial feature of pancreatic cancer and therefore its main components, RAF, MEK and ERK kinases, have been targeted pharmacologically, largely by small-molecule inhibitors. The recent advances in the development of inhibitors not only directly targeting the RAF/MEK/ERK pathway but also indirectly through inhibition of its regulators, such as Src homology-containing protein tyrosine phosphatase 2 (SHP2) and Son of sevenless homolog 1 (SOS1), provide new therapeutic opportunities. Moreover, the discovery of allele-specific small-molecule inhibitors against mutant KRAS variants has brought excitement for successful innovations in the battle against pancreatic cancer. Herein, we review the recent advances in targeted therapy and combinatorial strategies with focus on the current preclinical and clinical approaches, providing critical insight, underscoring the potential of these efforts and supporting their promise to improve the lives of patients with PDAC.

Many faces, many places: delving deeper into CAF heterogeneity in NSCLC.

In a recent study published in Cancer Cell, Cords et al. employed multiplexed imaging mass cytometry to analyze cancer-associated fibroblast (CAF) heterogeneity in 1070 NSCLC patients. This work defined good and poor prognostic CAF phenotypes, the latter associated with metastasis and chemoresistance, as well as revealed that CAF spatial location correlates with immune cell infiltration and clinical outcome.

Triple MAPK inhibition salvaged a relapsed post-BCMA CAR-T cell therapy multiple myeloma patient with a BRAF V600E subclonal mutation.

BACKGROUND: Multiple Myeloma (MM) is a progressive plasma cell neoplasm characterized by heterogeneous clonal expansion. Despite promising response rates achieved with anti-BCMA CAR-T cell therapy, patients may still relapse and there are currently no clear therapeutic options in post-CAR-T settings. In this report, we present a case of a post-BCMA CAR-T relapsed/refractory (RR) MM patient with skin extramedullary disease (EMD) in which a novel MAPK inhibition combinatorial strategy was implemented based on next-generation sequencing and in vitro experiments. CASE PRESENTATION: A 61-year-old male with penta-refractory MM penta- (IgA lambda), ISS stage 3 with hyperdiploidy, gain of 1q21 and del13 was treated with anti-BCMA CAR-T cell therapy, achieving a best response of VGPR. He progressed after 6 months and was salvaged for a short period with autologous stem cell transplantation. Eventually, he progressed with extramedullary disease manifested as subcutaneous nodules. Based on whole-exome sequencing, we identified a BRAF (V600E) dominant subclone in both bone marrow and cutaneous plasmacytoma. Following in vitro experiments, and according to our previous studies, we implemented a triple MAPK inhibition strategy under which the patient achieved a very good partial response for 110 days, which allowed to bridge him to subsequent clinical trials and eventually achieve a stringent complete response (sCR). CONCLUSION: Here, we show the applicability, effectiveness, and tolerability the triple MAPK inhibition strategy in the context of post-BCMA CAR-T failure in specific subset of patients. The triple therapy could bridge our hospice bound RRMM patient with BRAF (V600E) to further therapeutic options where sCR was achieved. We will further evaluate triple MAPK inhibition in patients with BRAF V600E in a precision medicine clinical trial launching soon.

Distinct CDK6 complexes determine tumor cell response to CDK4/6 inhibitors and degraders.

CDK4/6 inhibitors (CDK4/6i) are effective in metastatic breast cancer, but they have been only modestly effective in most other tumor types. Here we show that tumors expressing low CDK6 rely on CDK4 function, and are exquisitely sensitive to CDK4/6i. In contrast, tumor cells expressing both CDK4 and CDK6 have increased reliance on CDK6 to ensure cell cycle progression. We discovered that CDK4/6i and CDK4/6 degraders potently bind and inhibit CDK6 selectively in tumors in which CDK6 is highly thermo-unstable and strongly associated with the HSP90/CDC37 complex. In contrast, CDK4/6i and CDK4/6 degraders are ineffective in antagonizing tumor cells expressing thermostable CDK6, due to their weaker binding to CDK6 in these cells. Thus, we uncover a general mechanism of intrinsic resistance to CDK4/6i and CDK4/6i-derived degraders and the need for novel inhibitors targeting the CDK4/6i-resistant, thermostable form of CDK6 for application as cancer therapeutics.

Exploiting Allosteric Properties of RAF and MEK Inhibitors to Target Therapy-Resistant Tumors Driven by Oncogenic BRAF Signaling.

Current clinical RAF inhibitors (RAFi) inhibit monomeric BRAF (mBRAF) but are less potent against dimeric BRAF (dBRAF). RAFi equipotent for mBRAF and dBRAF have been developed but are predicted to have lower therapeutic index. Here we identify a third class of RAFi that selectively inhibits dBRAF over mBRAF. Molecular dynamic simulations reveal restriction of the movement of the BRAF αC-helix as the basis of inhibitor selectivity. Combination of inhibitors based on their conformation selectivity (mBRAF- plus dBRAF-selective plus the most potent BRAF-MEK disruptor MEK inhibitor) promoted suppression of tumor growth in BRAFV600E therapy-resistant models. Strikingly, the triple combination showed no toxicities, whereas dBRAF-selective plus MEK inhibitor treatment caused weight loss in mice. Finally, the triple combination achieved durable response and improved clinical well-being in a patient with stage IV colorectal cancer. Thus, exploiting allosteric properties of RAF and MEK inhibitors enables the design of effective and well-tolerated therapies for BRAFV600E tumors. SIGNIFICANCE: This work identifies a new class of RAFi that are selective for dBRAF over mBRAF and determines the basis of their selectivity. A rationally designed combination of RAF and MEK inhibitors based on their conformation selectivity achieved increased efficacy and a high therapeutic index when used to target BRAFV600E tumors.See related commentary by Zhang and Bollag, p. 1620.This article is highlighted in the In This Issue feature, p. 1601.

Polycystin-1 induces activation of the PI3K/AKT/mTOR pathway and promotes angiogenesis in renal cell carcinoma.

In the present study we investigated the expression and the functional role of mechanosensitive polycystins in renal cell carcinoma (RCC). In 115 RCC patients we evaluated the protein expression of polycystin-1 (PC1), polycystin-2 (PC2), VEGF and protein components of the PI3K/Akt/mTOR pathway, which have been implicated both in RCC and polycystic kidney disease. PC1 and PC2 demonstrated reduced expression throughout the RCC tissue compared to the adjacent normal tissue. PC1 and PC2 revealed high expression when they were associated with higher grade and decreased 5-year survival respectively. PC1 and PC2 were positively correlated with p110γ subunit of PI3K and high PC1 expressing cells tended to display activation/phosphorylation of Akt. There was also a positive association between PC1 and VEGF expression, whereas PC1 augmented the tumor's microvascular network in stage IV carcinomas. In human RCC cells, functional inhibition of PC1 resulted in upregulation of the PI3K/Akt/mTOR pathway, enhanced cell proliferation and led to inhibition of cell migration. Conclusively, aberrant PC1 regulation is associated with increased angiogenesis and features of advanced disease in RCC tissues.

Differential Expression of Apoptotic and Low-Grade Inflammatory Markers in Alzheimer Disease Compared to Diabetes Mellitus Type 1 and 2.

BACKGROUND: Neuroinflammation, impaired brain insulin signaling, and neuronal apoptosis may be interrelated in the pathophysiology of people with Alzheimer disease (AD) and diabetes, either type 1 or 2 diabetes (T1D or T2D, respectively). METHODS: We studied 116 patients: 41 with AD, 20 with T1D, 21 with T2D, and 34 healthy controls. The number (n) of cytokine-secreting peripheral blood mononuclear cells (PBMCs) before and after mitogenic stimulation was determined for interleukin 1ß (IL1ß), interleukin 6 (IL6), tumor necrosis factor (TNF) by the enzyme-linked-immuno-spot assay. Serum concentrations of C-reactive protein (CRP) and Fas ligand (FASLG) were determined by ELISA. RESULTS: The studied subgroups did not differ in sex but differed in age. Higher CRP concentrations were detected in the AD group than in the T1D group (P = 0.02) and lower in controls (P < 0.001). The nPBMCs was higher in AD patients after stimulation than in basal conditions: after stimulation in nTNF (P < 0.001 vs T2D; P < 0.001 vs T1D; P = 0.001 vs control), nIL6 (P = 0.039 vs T2D; P < 0.001 vs T1D; P = 0.007 vs control), and nIL1ß (P = 0.03 vs control). The nPBMCs increased after stimulation with ΡΜA in all the subgroups (P < 0.001). FASLG in the AD group displayed statistically higher concentrations than in all other subgroups (P < 0.001 vs T2D; P < 0.001 vs T1D; P = 0.012 vs control). The nPBMCs was positively correlated with plasma concentrations of FASLG in the AD subgroup. CONCLUSIONS: Patients with AD display a low-grade systemic inflammation compared to people with diabetes. The FAS-FASLG pathway has a potential role because FASLG concentrations are positively correlated with the inflammatory response in AD. However, this positive correlation cannot be seen in people with diabetes, at least not with the apoptotic markers used in the present study.

SHP2 Drives Adaptive Resistance to ERK Signaling Inhibition in Molecularly Defined Subsets of ERK-Dependent Tumors.

Pharmacologic targeting of components of ERK signaling in ERK-dependent tumors is often limited by adaptive resistance, frequently mediated by feedback-activation of RTK signaling and rebound of ERK activity. Here, we show that combinatorial pharmacologic targeting of ERK signaling and the SHP2 phosphatase prevents adaptive resistance in defined subsets of ERK-dependent tumors. In each tumor that was sensitive to combined treatment, p(Y542)SHP2 induction was observed in response to ERK signaling inhibition. The strategy was broadly effective in TNBC models and tumors with RAS mutations at G12, whereas tumors with RAS(G13D) or RAS(Q61X) mutations were resistant. In addition, we identified a subset of BRAF(V600E) tumors that were resistant to the combined treatment, in which FGFR was found to drive feedback-induced RAS activation, independently of SHP2. Thus, we identify molecular determinants of response to combined ERK signaling and SHP2 inhibition in ERK-dependent tumors.

Potential of glycative stress targeting for cancer prevention.

Glycative stress from endogenous and exogenous advanced glycation end-products (AGEs) has been implicated to cancer development and progression. Dicarbonyl compounds, the main AGE precursors and crosslinked AGE forms may directly react with proteins, lipids and nucleic acids, modify their structure and affect tissue microenvironment. They may also induce elevation of reactive oxygen species (ROS) and enhance cellular oxidative stress, an important regulator of cancer hallmarks. Moreover, the activation of AGE-receptor for AGE (RAGE) signalling pathways mediates inflammation, oxidative stress, autophagy and apoptosis leading to genomic instability and cancer initiation. Here, we provide evidence on the impact of glycative stress in promoting human tumorigenesis and we discuss the potential application of anti-glycating agents, RAGE and glyoxalase-1 inhibitors in cancer prevention.

Mechanosensor polycystin-1 potentiates differentiation of human osteoblastic cells by upregulating Runx2 expression via induction of JAK2/STAT3 signaling axis.

Polycystin-1 (PC1) has been proposed as a chief mechanosensing molecule implicated in skeletogenesis and bone remodeling. Mechanotransduction via PC1 involves proteolytic cleavage of its cytoplasmic tail (CT) and interaction with intracellular pathways and transcription factors to regulate cell function. Here we demonstrate the interaction of PC1-CT with JAK2/STAT3 signaling axis in mechanically stimulated human osteoblastic cells, leading to transcriptional induction of Runx2 gene, a master regulator of osteoblastic differentiation. Primary osteoblast-like PC1-expressing cells subjected to mechanical-stretching exhibited a PC1-dependent increase of the phosphorylated(p)/active form of JAK2. Specific interaction of PC1-CT with pJAK2 was observed after stretching while pre-treatment of cells with PC1 (anti-IgPKD1) and JAK2 inhibitors abolished JAK2 activation. Consistently, mechanostimulation triggered PC1-mediated phosphorylation and nuclear translocation of STAT3. The nuclear phosphorylated(p)/DNA-binding competent pSTAT3 levels were augmented after stretching followed by elevated DNA-binding activity. Pre-treatment with a STAT3 inhibitor either alone or in combination with anti-IgPKD1 abrogated this effect. Moreover, PC1-mediated mechanostimulation induced elevation of Runx2 mRNA levels. ChIP assays revealed direct regulation of Runx2 promoter activity by STAT3/Runx2 after mechanical-stretching that was PC1-dependent. Our findings show that mechanical load upregulates expression of Runx2 gene via potentiation of PC1-JAK2/STAT3 signaling axis, culminating to possibly control osteoblastic differentiation and ultimately bone formation.

Recent Advances in Mechanobiology of Osteosarcoma.

Mechanotransduction is a key process by which cells perceive extracellular mechanical cues/intercellular physical interactions and transform them into intracellular biochemical signals. This physiological process is crucial during bone development and bone remodeling throughout childhood and adult life, whereas several aberrations during this process have emerged as a distinct pathogenic molecular entity in bone maladies and tumor formation. The present review focuses on recent advances regarding the mechanobiology of osteosarcoma, the most common type of bone cancer. Special emphasis is given on the mechano-responsive signal transduction pathways underlying osteosarcoma pathology and on specific mechanosensitive molecules engaged in osteosarcoma development. J. Cell. Biochem. 118: 232-236, 2017. © 2016 Wiley Periodicals, Inc.

RANKL Signaling and ErbB Receptors in Breast Carcinogenesis.

ErbB family members, ErbB1/EGFR/HER-1, ErbB2/HER-2, ErbB3/HER-3 and ErbB4/HER-4, have been implicated in breast cancer (BC) tumorigenicity. Recently, crucial roles for RANK/RANKL signaling in addition to key downstream factor NF-κB have been demonstrated in mammary tumorigenesis. Here, we present the hypothesis of a novel association between ErbB and RANK pathways in promoting BC. The proposed model alludes to the cross-talk that might occur between RANK and ErbB receptors. This interplay might regulate RANK signaling and consequently, modulate carcinogenesis, mainly in ErbB2 over-expressing BC cells. Thus, we highlight the significance of the RANK/RANKL axis as a putative therapeutic target in this malignancy, and furthermore, suggest that the combination of ErbB and RANK/RANKL inhibitors may have therapeutic benefit for certain BC patients.

Pivotal role of high-mobility group box 1 (HMGB1) signaling pathways in glioma development and progression.

Human gliomas represent the most common type of intracranial tumors, with highest morbidity and mortality. They are characterized by excessive invasiveness and cell proliferation while their unclear boundaries predispose to tumor recurrence soon after conventional treatment. Elucidation of the molecular mechanisms implicated in their development and/or treatment resistance is highly demanded. The high-mobility group box 1 (HMGB1) protein, a highly conserved nuclear protein that functions as a chromatin-binding factor, facilitating nucleosome stabilization and regulating gene transcription, has been implicated in glioma formation and progression. Extracellular released HMGB1 binds to high-affinity receptors, including the receptor for advanced glycation end-products (RAGE) and toll-like receptor (TLR)-2, TLR-4, and TLR-9. Upon receptor binding, HMGB1 triggers the activation of key signaling pathways and immune responses, involved in the regulation of cell growth, differentiation, motility, and apoptosis. Based on the type of receptor and/or cell, HMGB1 is capable to promote oncogenesis or suppress tumor growth, thus affecting treatment efficacy. Herein, we discuss recent evidence implicating HMGB1 in glioma cell differentiation, proliferation, and metastasis with both clinical and prognostic significance. In addition, potential therapeutic approaches to target this protein in order to reduce chemoresistance of glioma cells are also addressed.

Deciphering signaling networks in osteosarcoma pathobiology.

Osteosarcoma is the most frequent type of primary bone tumors among children and adolescents. During the past years, little progress has been made regarding prognosis of osteosarcoma patients, especially for those with metastatic disease. Genomic instability and gene alterations are common, but current data do not reveal a consistent and repeatable pattern of osteosarcoma development, thus paralleling the tumor's high heterogeneity. Critical signal transduction pathways have been implicated in osteosarcoma pathobiology and are being evaluated as therapeutic targets, including receptor activator for nuclear factor-κB (RANK), Wnt, Notch, phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin, and mechanotransduction pathways. Herein, we recapitulate and discuss recent advances in the context of molecular mechanisms and signaling networks that contribute to osteosarcoma progression and metastasis, towards patient-tailored and novel-targeted treatments.

Clinical significance of AGE-RAGE axis in colorectal cancer: associations with glyoxalase-I, adiponectin receptor expression and prognosis.

BACKGROUND: Advanced glycation end products (AGEs) and their receptor RAGE emerge as important pathogenic contributors in colorectal carcinogenesis. However, their relationship to the detoxification enzyme Glyoxalase (GLO)-I and Adiponectin receptors (AdipoR1, AdipoR2) in colorectal carcinoma (CRC) is currently understudied. In the present study, we investigated the expression levels of the above molecules in CRC compared to adjacent non-tumoral tissue and their potential correlation with clinicopathological characteristics and patients' survival. METHODS: We analyzed the immunohistochemical expression of AGE, RAGE, GLO-1, AdipoR1 and AdipoR2 in 133 primary CRC cases, focusing on GLO-I. The tumour MSI status was further assessed in mucinous carcinomas. Western immunoblotting was employed for validation of immunohistochemical data in normal and tumoral tissues as well in three CRC cell lines. An independent set of 55 patients was also used to validate the results of univariate survival analysis regarding GLO-I. RESULTS: CRC tissue showed higher intensity of both AGE and RAGE expression compared with normal colonic mucosa which was negative for GLO-I in most cases (78 %). Western immunoblotting confirmed AGE, RAGE and GLO-I overexpression in tumoral tissue. GLO-I expression was directly related to RAGE and inversely related to AGE immunolabeling. There was a trend towards higher expression of all markers (except for RAGE) in the subgroup of mucinous carcinomas which, although of borderline significance, seemed to be more prominent for AdipoR1 and AGE. Additionally, AGE, AdipoR1 and Adipo R2 expression was related to tumor grade, whereas GLO-1 and AdipoR1 to T-category. In survival analysis, AdipoR2 and GLO-I overexpression predicted shortened survival in the entire cohort and in early stage cases, an effect which for GLO-I was reproduced in the validation cohort. Moreover, GLO-I emerged as an independent prognosticator of adverse significance in the patients' cohort. CONCLUSIONS: We herein provide novel evidence regarding the possible interactions between the components of AGE-RAGE axis, GLO-I and adiponectin receptors in CRC. AGE and AdipoR1 are possibly involved in colorectal carcinogenesis, whereas AdipoR2 and GLO-I emerged as novel independent prognostic biomarkers of adverse significance for patients with early disease stage. Further studies are warranted to extend our observations and investigate their potential therapeutic significance.