Paradoxical oncogenesis--the long-term effects of BRAF inhibition in melanoma

RAF1 gene fusions are recurrent driver events in infantile fibrosarcoma-like mesenchymal tumors

Infantile fibrosarcomas (IFS) and congenital mesoblastic nephroma (CMN) are rare myofibroblastic tumors of infancy and early childhood commonly harboring the ETV6::NTRK3 gene fusion. IFS/CMN are considered as tumors with an 'intermediate prognosis' as they are locally aggressive, but rarely metastasize, and generally have a favorable outcome. A fraction of IFS/CMN-related neoplasms are negative for the ETV6::NTRK3 gene rearrangement and are characterized by other chimeric proteins promoting MAPK signaling upregulation. In a large proportion of these tumors, which are classified as IFS-like mesenchymal neoplasms, the contributing molecular events remain to be identified. Here, we report three distinct rearrangements involving RAF1 among eight ETV6::NTRK3 gene fusion-negative tumors with an original histological diagnosis of IFS/CMN. The three fusion proteins retain the entire catalytic domain of the kinase. Two chimeric products, GOLGA4::RAF1 and LRRFIP2::RAF1, had previously been reported as driver events in different cancers, whereas the third, CLIP1::RAF1, represents a novel fusion protein. We demonstrate that CLIP1::RAF1 acts as a bona fide oncoprotein promoting cell proliferation and migration through constitutive upregulation of MAPK signaling. We show that the CLIP1::RAF1 hyperactive behavior does not require RAS activation and is mediated by constitutive 14-3-3 protein-independent dimerization of the chimeric protein. As previously reported for the ETV6::NTRK3 fusion protein, CLIP1::RAF1 similarly upregulates PI3K-AKT signaling. Our findings document that RAF1 gene rearrangements represent a recurrent event in ETV6::NTRK3-negative IFS/CMN and provide a rationale for the use of inhibitors directed to suppress MAPK and PI3K-AKT signaling in these cancers. © 2024 The Pathological Society of Great Britain and Ireland.

Pulmonary BRAF-driven Langerhans cell histiocytosis following selpercatinib use in metastatic medullary thyroid cancer

Summary

RET mutations are implicated in 60% of medullary thyroid cancer (MTC) cases. The RET-selective tyrosine kinase inhibitor selpercatinib is associated with unprecedented efficacy compared to previous multi-kinase treatments. Langerhans cell histiocytosis (LCH) is a clonal histiocytic neoplasm usually driven by somatic BRAF mutations, resulting in dysregulated MAPK signalling. We describe a 22-year-old woman with metastatic MTC to regional lymph nodes, lung and liver. Tumour tissue harboured a somatic pathogenic RET variant p.(M918T) and selpercatinib was commenced. She experienced sustained clinical, biochemical and radiological responses. Two years later, she developed rapidly progressive apical lung nodules, prompting biopsy. Histopathology demonstrated LCH with a rare BRAF variant p.(V600_K601>D). The lung nodules improved with inhaled corticosteroids. We hypothesize that selective pressure from RET blockade may have activated a downstream somatic BRAF mutation, resulting in pulmonary LCH. We recommend continued vigilance for neoplasms driven by dysregulated downstream MAPK signalling in patients undergoing selective RET inhibition.

Learning points

Patients with RET-altered MTC can experience rapid disease improvement and sustained disease stability with selective RET blockade (selpercatinib). LCH is a clonal neoplasm driven by MAPK activation, for which the most common mechanism is BRAF mutation. Both MTC and pulmonary LCH are driven by dysregulated MAPK signalling pathway activation. We hypothesise that the RET-specific inhibitor selpercatinib may have caused the activation of dormant LCH secondary to selective pressure and clonal proliferation.

Pediatric low-grade glioma: State-of-the-art and ongoing challenges

The most common childhood central nervous system (CNS) tumor is pediatric low-grade glioma (pLGG), representing 30%-40% of all CNS tumors in children. Although there is high associated morbidity, tumor-related mortality is relatively rare. pLGG is now conceptualized as a chronic disease, underscoring the importance of functional outcomes and quality-of-life measures. A wealth of data has emerged about these tumors, including a better understanding of their natural history and their molecular drivers, paving the way for the use of targeted inhibitors. While these treatments have heralded tremendous promise, challenges remain about how to best optimize their use, and the long-term toxicities associated with these inhibitors remain unknown. The International Pediatric Low-Grade Glioma Coalition (iPLGGc) is a global group of physicians and scientists with expertise in pLGG focused on addressing key pLGG issues. Here, the iPLGGc provides an overview of the current state-of-the-art in pLGG, including epidemiology, histology, molecular landscape, treatment paradigms, survival outcomes, functional outcomes, imaging response, and ongoing challenges. This paper also serves as an introduction to 3 other pLGG manuscripts on (1) pLGG preclinical models, (2) consensus framework for conducting early-phase clinical trials in pLGG, and (3) pLGG resistance, rebound, and recurrence.

Phytocompounds from essential oil of Mentha aquatica L. cv. Lime prevent vemurafenib-promoted skin carcinogenesis via inhibiting HRASQ61L keratinocytes and reprogramming macrophage activities

BACKGROUND

Twenty to thirty percent of patients taking BRAF inhibitors such as vemurafenib (PLX4032) for melanoma develop cutaneous squamous cell carcinomas.

PURPOSE

This study aimed to elucidate the chemopreventive effect of essential oil from Mentha aquatica L. cv. Lime (EO) and its major constituents, limonene and carvone (L + C) that made up 45.68% of the EO, against PLX4032-induced cutaneous side effects.

METHODS

PLX4032 accelerated skin papilloma formation and keratinocyte HRAS mutation in 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced two-stage skin carcinogenesis mouse model was used to evaluate the in vivo bioefficacy of EO and L + C. The effects and molecular mechanisms of EO and L + C on deregulating mouse PDVHRASQ61L keratinocyte activities were demonstrated using a spectrum of bioactivity assays, western blotting, immunochemistry, and keratinocyte-macrophage co-culture assay.

RESULTS

Treatment with EO suppressed colony formation ability, cell migration, invasion, and induced G2/M cell-cycle arrest and apoptosis in PDVHRASQ61L keratinocytes, and L + C treatment inhibited colony formation, cell migration and invasion of PDV cells. In mouse skin irritated with DMBA/TPA (DT group) or DMBA/TPA with PLX4032 (DTP group), topical application of EO and L + C significantly delayed papilloma appearance and reduced papilloma incidence compared to DT or DTP controls. Histopathology results showed that EO and L + C treatment attenuated K14+ keratinocyte proliferation and paradoxical MAPK activation, and shifted the macrophage population from M2 (CD163+) to M1 (iNOS+) in the mouse skin microenvironment. The conditioned medium of EO or L + C pre-treated PDV keratinocytes promoted M0 macrophages to differentiate from THP-1 cells into M1-like macrophages.

CONCLUSION

This study demonstrates that EO and L + C in combination prevent PLX4032-induced cutaneous side-effects and skin carcinogenesis in mice through reprogramming the macrophage cell population and inhibiting keratinocyte activity. Both mint EO and the natural products L + C can be considered to be effective chemopreventive agents that might be useful in reducing cutaneous lesions in human patients administrated with BRAF inhibitors.

Targeting the RAS/RAF/MAPK pathway for cancer therapy: from mechanism to clinical studies

Metastatic dissemination of solid tumors, a leading cause of cancer-related mortality, underscores the urgent need for enhanced insights into the molecular and cellular mechanisms underlying metastasis, chemoresistance, and the mechanistic backgrounds of individuals whose cancers are prone to migration. The most prevalent signaling cascade governed by multi-kinase inhibitors is the mitogen-activated protein kinase (MAPK) pathway, encompassing the RAS-RAF-MAPK kinase (MEK)-extracellular signal-related kinase (ERK) pathway. RAF kinase is a primary mediator of the MAPK pathway, responsible for the sequential activation of downstream targets, such as MEK and the transcription factor ERK, which control numerous cellular and physiological processes, including organism development, cell cycle control, cell proliferation and differentiation, cell survival, and death. Defects in this signaling cascade are associated with diseases such as cancer. RAF inhibitors (RAFi) combined with MEK blockers represent an FDA-approved therapeutic strategy for numerous RAF-mutant cancers, including melanoma, non-small cell lung carcinoma, and thyroid cancer. However, the development of therapy resistance by cancer cells remains an important barrier. Autophagy, an intracellular lysosome-dependent catabolic recycling process, plays a critical role in the development of RAFi resistance in cancer. Thus, targeting RAF and autophagy could be novel treatment strategies for RAF-mutant cancers. In this review, we delve deeper into the mechanistic insights surrounding RAF kinase signaling in tumorigenesis and RAFi-resistance. Furthermore, we explore and discuss the ongoing development of next-generation RAF inhibitors with enhanced therapeutic profiles. Additionally, this review sheds light on the functional interplay between RAF-targeted therapies and autophagy in cancer.

Long-term outcomes and persistent toxicities following BRAF/MEK inhibitor therapy for advanced melanoma

BACKGROUND

Recent studies have shown that approximately 20% of patients have 4-5 year progression free survival (PFS) on BRAF/MEK inhibitors. The long-term safety and efficacy in these patients with more durable responses have not been studied.

METHODS

This retrospective multicenter cohort study assessed response, progression, and adverse events in patients from eight institutions in four countries with >4-year PFS following BRAF/MEK inhibitors.

RESULTS

Among 146 patients, 112 (76.7%) remained progression-free at median follow-up of 7.8 years from treatment start; 131 (89.7%) were alive. Among progressors (n = 34), 21 (62%) were on treatment at progression. Among those who discontinued treatment for reasons other than progression (toxicity, preference, etc.) (n = 68, with median 49 months treatment duration), 13 (19%) progressed (median 15.3 months from treatment cessation to progression). Surgery or radiation for single-organ progression resulted in durable benefit in 11 of 22 patients (50%). Subsequent systemic therapy included immune therapy (24% responded) and BRAF/MEK rechallenge (56% responded). Thirteen (8.9%) patients had ongoing toxicities at last follow-up, 10 (77%) of which remained on active treatment; all cardiac adverse events had resolved (n = 9). Twenty-four (16.4%) patients developed any new primary cancer, and 28 (19%) patients experienced other major health events.

CONCLUSIONS

Over 75% of patients with 4-year PFS from BRAF/MEK inhibitors had continued durable antitumor responses after nearly 8-year median follow-up, with similar results in patients who discontinued therapy for reasons other than progression. Long-term toxicities were uncommon and low-grade. These findings highlight the often-favourable outcomes in patients with extended benefit from BRAF/MEK inhibitors.

Theoretical analysis reveals a role for RAF conformational autoinhibition in paradoxical activation

RAF kinase inhibitors can, under certain conditions, increase RAF kinase signaling. This process, which is commonly referred to as 'paradoxical activation' (PA), is incompletely understood. We use mathematical and computational modeling to investigate PA and derive rigorous analytical expressions that illuminate the underlying mechanism of this complex phenomenon. We find that conformational autoinhibition modulation by a RAF inhibitor could be sufficient to create PA. We find that experimental RAF inhibitor drug dose-response data that characterize PA across different types of RAF inhibitors are best explained by a model that includes RAF inhibitor modulation of three properties: conformational autoinhibition, dimer affinity, and drug binding within the dimer (i.e., negative cooperativity). Overall, this work establishes conformational autoinhibition as a robust mechanism for RAF inhibitor-driven PA based solely on equilibrium dynamics of canonical interactions that comprise RAF signaling and inhibition.

Challenges and Opportunities in the Crusade of BRAF Inhibitors: From 2002 to 2022

Serine/threonine-protein kinase B-Raf (BRAF; RAF = rapidly accelerated fibrosarcoma) plays an important role in the mitogen-activated protein kinase (MAPK) signaling cascade. Somatic mutations in the BRAF gene were first discovered in 2002 by Davies et al., which was a major breakthrough in cancer research. Subsequently, three different classes of BRAF mutants have been discovered. This class includes class I monomeric mutants (BRAFV600), class II BRAF homodimer mutants (non-V600), and class III BRAF heterodimers (non-V600). Cancers caused by these include melanoma, thyroid cancer, ovarian cancer, colorectal cancer, nonsmall cell lung cancer, and others. In this study, we have highlighted the major binding pockets in BRAF protein, their active and inactive conformations with inhibitors, and BRAF dimerization and its importance in paradoxical activation and BRAF mutation. We have discussed the first-, second-, and third-generation drugs approved by the Food and Drug Administration and drugs under clinical trials with all four different binding approaches with DFG-IN/OUT and αC-IN/OUT for BRAF protein. We have investigated particular aspects and difficulties with all three generations of inhibitors. Finally, this study has also covered recent developments in synthetic BRAF inhibitors (from their discovery in 2002 to 2022), their unique properties, and importance in inhibiting BRAF mutants.

Phase 1 study of the pan-RAF inhibitor tovorafenib in patients with advanced solid tumors followed by dose expansion in patients with metastatic melanoma

PURPOSE

Genomic alterations of BRAF and NRAS are oncogenic drivers in malignant melanoma and other solid tumors. Tovorafenib is an investigational, oral, selective, CNS-penetrant, small molecule, type II pan‑RAF inhibitor. This first-in-human phase 1 study explored the safety and antitumor activity of tovorafenib.

METHODS

This two-part study in adult patients with relapsed or refractory advanced solid tumors included a dose escalation phase and a dose expansion phase including molecularly defined cohorts of patients with melanoma. Primary objectives were to evaluate the safety of tovorafenib administered once every other day (Q2D) or once weekly (QW), and to determine the maximum-tolerated and recommended phase 2 dose (RP2D) on these schedules. Secondary objectives included evaluation of antitumor activity and tovorafenib pharmacokinetics.

RESULTS

Tovorafenib was administered to 149 patients (Q2D n = 110, QW n = 39). The RP2D of tovorafenib was defined as 200 mg Q2D or 600 mg QW. In the dose expansion phase, 58 (73%) of 80 patients in Q2D cohorts and 9 (47%) of 19 in the QW cohort had grade ≥ 3 adverse events. The most common of these overall were anemia (14 patients, 14%) and maculo-papular rash (8 patients, 8%). Responses were seen in 10 (15%) of 68 evaluable patients in the Q2D expansion phase, including in 8 of 16 (50%) patients with BRAF mutation-positive melanoma naïve to RAF and MEK inhibitors. In the QW dose expansion phase, there were no responses in 17 evaluable patients with NRAS mutation-positive melanoma naïve to RAF and MEK inhibitors; 9 patients (53%) had a best response of stable disease. QW dose administration was associated with minimal accumulation of tovorafenib in systemic circulation in the dose range of 400-800 mg.

CONCLUSIONS

The safety profile of both schedules was acceptable, with QW dosing at the RP2D of 600 mg QW preferred for future clinical studies. Antitumor activity of tovorafenib in BRAF-mutated melanoma was promising and justifies continued clinical development across multiple settings.

CLINICALTRIALS

GOV IDENTIFIER

NCT01425008.

Preventing skin toxicities induced by EGFR inhibitors by topically blocking drug-receptor interactions

Epidermal growth factor receptor (EGFR) inhibitors are used to treat many advanced-stage epithelial cancers but induce severe skin toxicities in most treated patients. These side effects lead to a deterioration in the quality of life of the patients and compromise the anticancer treatment. Current treatment strategies for these skin toxicities focus on symptom reduction rather than preventing the initial trigger that causes the toxicity. In this study, we developed a compound and method for treating "on-target" skin toxicity by blocking the drug at the site of toxicity without reducing the systemic dose reaching the tumor. We first screened for small molecules that effectively blocked the binding of anti-EGFR monoclonal antibodies to EGFR and identified a potential candidate, SDT-011. In silico docking predicted that SDT-011 interacted with the same residues on EGFR found to be important for the binding of EGFR inhibitors cetuximab and panitumumab. Binding of SDT-011 to EGFR reduced the binding affinity of cetuximab to EGFR and could reactivate EGFR signaling in keratinocyte cell lines, ex vivo cetuximab-treated whole human skin, and A431-injected mice. Specific small molecules were topically applied and were delivered via a slow-release system derived from biodegradable nanoparticles that penetrate the hair follicles and sebaceous glands, within which EGFR is highly expressed. Our approach has the potential to reduce skin toxicity caused by EGFR inhibitors.

A Putative Role of Candida albicans in Promoting Cancer Development: A Current State of Evidence and Proposed Mechanisms

Candida albicans is a commensal fungal species that commonly colonizes the human body, but it is also a pervasive opportunistic pathogen in patients with malignant diseases. A growing body of evidence suggests that this fungus is not only coincidental in oncology patients, but may also play an active role in the development of cancer. More specifically, several studies have investigated the potential association between C. albicans and various types of cancer, including oral, esophageal, and colorectal cancer, with a possible role of this species in skin cancer as well. The proposed mechanisms include the production of carcinogenic metabolites, modulation of the immune response, changes in cell morphology, microbiome alterations, biofilm production, the activation of oncogenic signaling pathways, and the induction of chronic inflammation. These mechanisms may act together or independently to promote cancer development. Although more research is needed to fully grasp the potential role of C. albicans in carcinogenesis, the available evidence suggests that this species may be an active contributor and underscores the importance of considering the impact of the human microbiome on cancer pathogenesis. In this narrative review, we aimed to summarize the current state of evidence and offer some insights into proposed mechanisms.

Spectrum of second primary malignancies and cause-specific mortality in pediatric and adult langerhans cell histiocytosis

With the advent of targeted therapeutics in Langerhans cell histiocytosis (LCH), there is a growing survivor population that might be at risk for late mortality from non-LCH causes, including second primary malignancies (SPMs). We undertook a large study using the Surveillance, Epidemiology, and End Results (SEER) database to evaluate the patterns of SPMs and cause-specific mortality among individuals with LCH (2000-2016) from the US. We found an increased risk of SPMs in the cohort (standardized incidence ratio [SIR] 2.07). The pediatric group was at a high risk of developing Hodgkin lymphoma (SIR 60.93) and non-Hodgkin lymphoma (SIR 60.88). People with adult-onset LCH were found to have a high risk of developing miscellaneous malignant cancers (SIR 11.43), which primarily included myelodysplastic syndrome. Adults were also at a high risk of developing carcinoma in-situ of vulva at 2-11 months [SIR 62.72] and B-ALL at 60-119 months [SIR 66.29] after LCH diagnosis. Additionally, 5% and 1% of the patients developed prior or concomitant malignancies with LCH, respectively. The 5 yr overall survival (OS) was 96.6% for pediatric and 88.5% for adult LCH cohorts. Most common cause of death was infections in pediatric and SPMs in adult LCH. Our study highlights that despite advances in treatments, people with LCH have an increased mortality risk from non-LCH causes when compared with the general population, including a high risk of SPMs.

RAS: Circuitry and therapeutic targeting

Cancer has affected the lives of millions worldwide and is truly regarded as a devastating disease process. Despite advanced understanding of the genomic underpinning of cancer development and progression, therapeutic challenges are still persistent. Among all the human cancers, around 33% are attributed to mutations in RAS oncogene, a crucial component of the signaling pathways. With time, our understanding of RAS circuitry has improved and now the fact that it activates several downstream effectors, depending on the type and grades of cancer has been established. The circuitry is controlled via post-transcriptional mechanisms and frequent distortions in these mechanisms lead to important metabolic as well as immunological states that favor cancer cells' growth, survival, plasticity and metastasis. Therefore, understanding RAS circuitry can help researchers/clinicians to develop novel and potent therapeutics that, in turn, can save the lives of patients suffering from RAS-mutant cancers. There are many challenges presented by resistance and the potential strategies with a particular focus on novel combinations for overcoming these, that could move beyond transitory responses in the direction of treatment. Here in this review, we will look at how understanding the circuitry of RAS can be put to use in making strategies for developing therapeutics against RAS- driven malignancies.

Molecular Features of Preinvasive and Invasive Vulvar Neoplasms

OBJECTIVES

Neoplasms arising from the vulva are uncommon and comprise various subtypes. Given the recent advancements in the molecular aspects of oncologic pathology and how they have impacted cancer treatment, an understanding of recent innovations in the molecular features of vulvar lesions is important.

MATERIALS AND METHODS

Systematic literature search was performed on PubMed, Google Scholar, and Scopus databases for molecular and genetic characteristics of vulvar neoplasms. Peer-reviewed literature published in English is included.

RESULTS

Squamous cell carcinoma (SCC) and its precursors are the predominant neoplasm at this site. Human papillomavirus (HPV) plays a crucial role in the pathogenesis of some of these lesions. Human papillomavirus-associated SCC follows the carcinogenic pathway driven by viral proteins E6 and E7 while HPV-independent SCC shows a high incidence of mutation of TP53 and CDKN2A genes. Mutations in the genes involving the PI3K-Akt pathway play an important role in the pathogenesis of both types of SCC. Among other vulvar malignancies, melanoma, and vulvar Paget disease (VPD) pose a significant clinical challenge and have unique molecular characteristics. Compared with dermal cutaneous melanoma, vulvar melanoma shows a higher rate of mutation of cKIT and NRAS genes and a lower rate of mutations in BRAF . Less than 20% of VPD shows amplification of ERBB2 and seldom shows mutation in genes involving the PI3K-Akt pathway.

CONCLUSIONS

Several potentially targetable molecular pathways have emerged as they have been shown to be involved in the tumorigenesis of SCC, melanoma, and VPD.

BRAF and MEK Targeted Therapies in Pediatric Central Nervous System Tumors

Simple Summary

This review is divided into two parts. The first analyzes the mechanisms of two important cellular pathways that are involved in tumoral proliferation, differentiation, migration, and angiogenesis: RAS/RAF/MEK/MAPK and PI3K/AKT/mTOR. The second part focuses on the currently available experience regarding targeted therapies against the mitogen-activated protein kinase (MAPK) pathway in pediatric CNS tumors, with the hope of offering a practical guide for consultation.

Abstract

BRAF is a component of the MAPK and PI3K/AKT/mTOR pathways that play a crucial role in cellular proliferation, differentiation, migration, and angiogenesis. Pediatric central nervous system tumors very often show mutations of the MAPK pathway, as demonstrated by next-generation sequencing (NGS), which now has an increasing role in cancer diagnostics. The MAPK mutated pathway in pediatric CNS tumors is the target of numerous drugs, approved or under investigation in ongoing clinical trials. In this review, we describe the main aspects of MAPK and PI3K/AKT/mTOR signaling pathways, with a focus on the alterations commonly involved in tumorigenesis. Furthermore, we reported the main available data about current BRAF and MEK targeted therapies used in pediatric low-grade gliomas (pLLGs), pediatric high-grade gliomas (pHGGs), and other CNS tumors that often present BRAF or MEK mutations. Further molecular stratification and clinical trial design are required for the treatment of pediatric CNS tumors with BRAF and MEK inhibitors.

Immunomodulatory Properties of PI3K/AKT/mTOR and MAPK/MEK/ERK Inhibition Augment Response to Immune Checkpoint Blockade in Melanoma and Triple-Negative Breast Cancer

Hyperactivation of PI3K/AKT/mTOR and MAPK/MEK/ERK signaling pathways is commonly observed in many cancers, including triple-negative breast cancer (TNBC) and melanoma. Moreover, the compensatory upregulation of the MAPK/MEK/ERK pathway has been associated with therapeutic resistance to targeted inhibition of the PI3K/AKT/mTOR pathway, and vice versa. The immune-modulatory effects of both PI3K and MAPK inhibition suggest that inhibition of these pathways might enhance response to immune checkpoint inhibitors (ICIs). ICIs have become the standard-of-care for metastatic melanoma and are recently an option for TNBC when combined with chemotherapy, but alternative options are needed when resistance develops. In this review, we present the current mechanistic understandings, along with preclinical and clinical evidence, that outline the efficacy and safety profile of combinatorial or sequential treatments with PI3K inhibitors, MAPK inhibitors, and ICIs for treatment of malignant melanoma and metastatic TNBC. This approach may present a potential strategy to overcome resistance in patients who are a candidate for ICI therapy with tumors harboring either or both of these pathway-associated mutations.

Co-Treatment of Chloroquine and Trametinib Inhibits Melanoma Cell Proliferation and Decreases Immune Cell Infiltration

Autophagy is characterized as a cytoprotective process and inhibition of autophagy with medicinally active agents, such as chloroquine (CQ) is proposed as a prospective adjuvant therapy for cancer. Here, we examined the preclinical effects of CQ combined with the MEK inhibitor trametinib (TRA) on melanoma. We found that cotreatment of CQ and TRA markedly slowed melanoma growth induced in Tyr-CreER.BrafCa.Ptenfl/fl mice. Immunostaining showed that trametinib decreased Ki-67+ proliferating cells, and increased TUNEL+ apoptotic cells. The combo treatment induced a further decrease of Ki-67+ proliferating cells. Consistent with the in vivo findings, CQ and TRA inhibited melanoma cell proliferation in vitro, which was correlated by decreased cyclin D1 expression. In addition, we found that tissues treated with CQ and TRA had significantly decreased numbers of CD4+ and CD8+ T-lymphocytes and F4/80+ macrophages. Together, these results indicate that cotreatment of CQ and TRA decreases cancer cell proliferation, but also dampens immune cell infiltration. Further study is warranted to understand whether CQ-induced immune suppression inadvertently affects therapeutic benefits.

The Role of Extracellular Matrix Remodeling in Skin Tumor Progression and Therapeutic Resistance

The extracellular matrix remodeling in the skin results from a delicate balance of synthesis and degradation of matrix components, ensuring tissue homeostasis. These processes are altered during tumor invasion and growth, generating a microenvironment that supports growth, invasion, and metastasis. Apart from the cellular component, the tumor microenvironment is rich in extracellular matrix components and bound factors that provide structure and signals to the tumor and stromal cells. The continuous remodeling in the tissue compartment sustains the developing tumor during the various phases providing matrices and proteolytic enzymes. These are produced by cancer cells and stromal fibroblasts. In addition to fostering tumor growth, the expression of specific extracellular matrix proteins and proteinases supports tumor invasion after the initial therapeutic response. Lately, the expression and structural modification of matrices were also associated with therapeutic resistance. This review will focus on the significant alterations in the extracellular matrix components and the function of metalloproteinases that influence skin cancer progression and support the acquisition of therapeutic resistance.

Lyso-PAF, a biologically inactive phospholipid, contributes to RAF1 activation

Phospholipase A2, group VII (PLA2G7) is widely recognized as a secreted, lipoprotein-associated PLA2 in plasma that converts phospholipid platelet-activating factor (PAF) to a biologically inactive product Lyso-PAF during inflammatory response. We report that intracellular PLA2G7 is selectively important for cell proliferation and tumor growth potential of melanoma cells expressing mutant NRAS, but not cells expressing BRAF V600E. Mechanistically, PLA2G7 signals through its product Lyso-PAF to contribute to RAF1 activation by mutant NRAS, which is bypassed by BRAF V600E. Intracellular Lyso-PAF promotes p21-activated kinase 2 (PAK2) activation by binding to its catalytic domain and altering ATP kinetics, while PAK2 significantly contributes to S338-phosphorylation of RAF1 in addition to PAK1. Furthermore, the PLA2G7-PAK2 axis is also required for full activation of RAF1 in cells stimulated by epidermal growth factor (EGF) or cancer cells expressing mutant KRAS. Thus, PLA2G7 and Lyso-PAF exhibit intracellular signaling functions as key elements of RAS-RAF1 signaling.

The Current State of Treatment and Future Directions in Cutaneous Malignant Melanoma

Malignant melanoma is the leading cause of death among cutaneous malignancies. While its incidence is increasing, the most recent cancer statistics show a small but clear decrease in mortality rate. This trend reflects the introduction of novel and more effective therapeutic regimens, including the two cornerstones of melanoma therapy: immunotherapies and targeted therapies. Immunotherapies exploit the highly immunogenic nature of melanoma by modulating and priming the patient’s own immune system to attack the tumor. Treatments combining immunotherapies with targeted therapies, which disable the carcinogenic products of mutated cancer cells, have further increased treatment efficacy and durability. Toxicity and resistance, however, remain critical challenges to the field. The present review summarizes past treatments and novel therapeutic interventions and discusses current clinical trials and future directions.

Biology and Treatment Advances in Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (CSCC) is the second most common skin cancer diagnosed worldwide. CSCC is generally localized and managed with local therapies such as excision and/or radiotherapy. For patients with unresectable or metastatic disease, recent improvements in our understanding of the underlying biology have led to significant advancements in treatment approaches-including the use of immune checkpoint inhibition (ICI)-which have resulted in substantial gains in response and survival compared to traditional cytotoxic approaches. However, there is a lack of understanding of the biology underpinning CSCC in immunocompromised patients, in whom the risk of developing CSCC is hundreds of times higher compared to immunocompetent patients. Furthermore, current ICI approaches are associated with significant risk of graft rejection in organ transplant recipients who make up a significant proportion of immunocompromised patients. Ongoing scientific and clinical research efforts are needed in order to maintain momentum to increase our understanding and refine our therapeutic approaches for patients with CSCC.

Modulation of FLT3-ITD Localization and Targeting of Distinct Downstream Signaling Pathways as Potential Strategies to Overcome FLT3-Inhibitor Resistance

OBJECTIVES: Internal tandem duplications (ITDs) of the Fms-like tyrosine kinase 3 (FLT3) represent the most frequent molecular aberrations in acute myeloid leukemia (AML) and are associated with an inferior prognosis. The pattern of downstream activation by this constitutively activated receptor tyrosine kinase is influenced by the localization of FLT3-ITD depending on its glycosylation status. Different pharmacological approaches can affect FLT3-ITD-driven oncogenic pathways by the modulation of FLT3-ITD localization. AIMS: The objective of this study was to investigate the effects of N-glycosylation inhibitors (tunicamycin or 2-deoxy-D-glucose) or the histone deacetylase inhibitor valproic acid (VPA) on FLT3-ITD localization and downstream activity. We sought to determine the potential differences between the distinct FLT3-ITD variants, particularly concerning their susceptibility towards combined treatment by addressing either N-glycosylation and the heat shock protein 90 (HSP90) by 17-AAG, or by targeting the PI3K/AKT/mTOR pathway by rapamycin after treatment with VPA. METHODS: Murine Ba/F3 leukemia cell lines were stably transfected with distinct FLT3-ITD variants resulting in IL3-independent growth. These Ba/F3 FLT3-ITD cell lines or FLT3-ITD-expressing human MOLM13 cells were exposed to tunicamycin, 2-deoxy-D-glucose or VPA, and 17-AAG or rapamycin, and characterized in terms of downstream signaling by immunoblotting. FLT3 surface expression, apoptosis, and metabolic activity were analyzed by flow cytometry or an MTS assay. Proteome analysis by liquid chromatography–tandem mass spectrometry was performed to assess differential protein expression. RESULTS: The susceptibility of FLT3-ITD-expressing cells to 17-AAG after pre-treatment with tunicamycin or 2-deoxy-D-glucose was demonstrated. Importantly, in Ba/F3 cells that were stably expressing distinct FLT3-ITD variants that were located either in the juxtamembrane domain (JMD) or in the tyrosine kinase 1 domain (TKD1), response to the sequential treatments with tunicamycin and 17-AAG varied between individual FLT3-ITD motifs without dependence on the localization of the ITD. In all of the FLT3-ITD cell lines that were investigated, incubation with tunicamycin was accompanied by intracellular retention of FLT3-ITD due to the inhibition of glycosylation. In contrast, treatment of Ba/F3-FLT3-ITD cells with VPA was associated with a significant increase of FLT3-ITD surface expression depending on FLT3 protein synthesis. The allocation of FLT3 to different cellular compartments that was induced by tunicamycin, 2-deoxy-D-glucose, or VPA resulted in the activation of distinct downstream signaling pathways. Whole proteome analyses of Ba/F3 FLT3-ITD cells revealed up-regulation of the relevant chaperone proteins (e.g., calreticulin, calnexin, HSP90beta1) that are directly involved in the stabilization of FLT3-ITD or in its retention in the ER compartment. CONCLUSION: The allocation of FLT3-ITD to different cellular compartments and targeting distinct downstream signaling pathways by combined treatment with N-glycosylation and HSP90 inhibitors or VPA and rapamycin might represent new therapeutic strategies to overcome resistance towards tyrosine kinase inhibitors in FLT3-ITD-positive AML. The treatment approaches addressing N-glycosylation of FLT3-ITD appear to depend on patient-specific FLT3-ITD sequences, potentially affecting the efficacy of such pharmacological strategies.

Vemurafenib Drives Epithelial-to-Mesenchymal Transition Gene Expression in BRAF Inhibitor‒Resistant BRAFV600E/NRASQ61K Melanoma Enhancing Tumor Growth and Metastasis in a Bioluminescent Murine Model

BRAF inhibitor (BRAFi) resistance compromises long-term survivorship of patients with malignant melanoma, and mutant NRAS is a major mediator of BRAFi resistance. In this study, employing phenotypic and transcriptomic analysis of isogenic melanoma cells that differ only by NRAS mutational status (BRAFi-sensitive A375-BRAF^V600E/NRAS^Q61 vs. BRAFi-resistant A375-BRAF^V600E/NRAS^Q61K), we show that BRAFi (vemurafenib) treatment selectively targets BRAF^V600E/NRAS^Q61K cells upregulating epithelial-to-mesenchymal transition (EMT) gene expression, paradoxically promoting invasiveness and metastasis in vitro and in vivo. First, NanoString nCounter transcriptomic analysis identified the upregulation of specific gene expression networks (EMT and EMT to metastasis) as a function of NRAS^Q61K status. Strikingly, BRAFi treatment further exacerbated the upregulation of genes promoting EMT in BRAF^V600E/NRAS^Q61K cells (with opposing downregulation of EMT-driver genes in the BRAF^V600E/NRAS^Q61 genotype) as detected by EMT-focused RT² Profiler qPCR array analysis. In BRAF^V600E/NRAS^Q61K cells, BRAFi treatment enhanced proliferation and invasiveness, together with activation of phosphorylated protein kinase B (Ser473), with opposing phenotypic effects observable in BRAF^V600E/NRAS^Q61 cells displaying downregulation of phosphorylated protein kinase B and phosphorylated extracellular signal-regulated kinase 1/2. In a SCID mouse bioluminescent melanoma metastasis model, BRAFi treatment enhanced lung tumor burden imposed by BRAF^V600E/NRAS^Q61K cells while blocking BRAF^V600E/NRAS^Q61 metastasis. These preclinical data document the BRAFi-driven enhancement of tumorigenesis and metastasis in BRAFi-resistant human BRAF^V600E/NRAS^Q61K melanoma, a finding with potential clinical implications for patients with NRAS-driven BRAFi-resistant tumors receiving BRAFi treatment.

Progress on Ras/MAPK Signaling Research and Targeting in Blood and Solid Cancers

Simple Summary

The Ras-Raf-MEK-ERK signaling pathway is responsible for regulating cell proliferation, differentiation, and survival. Overexpression and overactivation of members within the signaling cascade have been observed in many solid and blood cancers. Research often focuses on targeting the pathway to disrupt cancer initiation and progression. We aimed to provide an overview of the pathway’s physiologic role and regulation, interactions with other pathways involved in cancer development, and mutations that lead to malignancy. Several blood and solid cancers are analyzed to illustrate the impact of the pathway’s dysregulation, stemming from mutation or viral induction. Finally, we summarized different approaches to targeting the pathway and the associated novel treatments being researched or having recently achieved approval.

Abstract

The mitogen-activated protein kinase (MAPK) pathway, consisting of the Ras-Raf-MEK-ERK signaling cascade, regulates genes that control cellular development, differentiation, proliferation, and apoptosis. Within the cascade, multiple isoforms of Ras and Raf each display differences in functionality, efficiency, and, critically, oncogenic potential. According to the NCI, over 30% of all human cancers are driven by Ras genes. This dysfunctional signaling is implicated in a wide variety of leukemias and solid tumors, both with and without viral etiology. Due to the strong evidence of Ras-Raf involvement in tumorigenesis, many have attempted to target the cascade to treat these malignancies. Decades of unsuccessful experimentation had deemed Ras undruggable, but recently, the approval of Sotorasib as the first ever KRas inhibitor represents a monumental breakthrough. This advancement is not without novel challenges. As a G12C mutant-specific drug, it also represents the issue of drug target specificity within Ras pathway; not only do many drugs only affect single mutational profiles, with few pan-inhibitor exceptions, tumor genetic heterogeneity may give rise to drug-resistant profiles. Furthermore, significant challenges in targeting downstream Raf, especially the BRaf isoform, lie in the paradoxical activation of wild-type BRaf by BRaf mutant inhibitors. This literature review will delineate the mechanisms of Ras signaling in the MAPK pathway and its possible oncogenic mutations, illustrate how specific mutations affect the pathogenesis of specific cancers, and compare available and in-development treatments targeting the Ras pathway.

Toxicity of combined targeted therapy and concurrent radiotherapy in metastatic melanoma patients: a single-center retrospective analysis

Supplemental Digital Content is available in the text.

The Eastern Cooperative Oncology Group consensus guidelines from 2016 recommend interruption of targeted therapy with BRAF- and MEK-inhibitors during radiotherapy with data being based mostly on BRAF monotherapy. The aim of this study is to provide data on the safety of concurrent radiotherapy and combination targeted therapy with BRAF- and MEK-inhibitors. A total of 32 patients with 51 sessions of radiotherapy from one center receiving concurrent radiotherapy and BRAF- and MEK- inhibitors were included. Radiotherapy-associated toxicities were retrospectively collected. Incidence was compared between three groups: (A) targeted therapy during radiotherapy with and, (B) without interruption, and (C) radiotherapy before the start of targeted therapy. Survival and local disease control were examined. Targeted therapy was interrupted during radiotherapy in 16, not interrupted in 14, and only started after radiotherapy in 21 sessions. Stereotactic radiotherapy was applied in 28 sessions, conventionally fractionated radiotherapy in 23. The brain was the most common site of irradiation (n = 36). Radiotherapy-associated toxicities occurred in 41.2% (n = 21) of sessions and did not differ significantly among the groups. Overall survival was 11.7 months and progression-free survival was 8.4 months. No increase in radiotherapy-associated toxicity was seen where combination targeted therapy was not interrupted during radiotherapy. Prospective clinical trials are warranted to support our findings.

Synthesis and anti-hepatocellular carcinoma activity of aminopyridinol-sorafenib hybrids

Sorafenib is recommended as the primary therapeutic drug for patients with hepatocellular carcinoma. To discover a new compound that avoids low response rates and toxic side effects that occur in sorafenib therapy, we designed and synthesized new hybrid compounds of sorafenib and 2,4,5-trimethylpyridin-3-ols. Compound 6 was selected as the best of 24 hybrids that inhibit each of the four Raf kinases. The anti-proliferative activity of 6 in HepG2, Hep3B, and Huh7 cell lines was slightly lower than that of sorafenib. However, in H6c7 and CCD841 normal epithelial cell lines, the cytotoxicity of 6 was much lower than that of sorafenib. In addition, similar to sorafenib, compound 6 inhibited spheroid forming ability of Hep3B cells in vitro and tumour growth in a xenograft tumour model of the chick chorioallantoic membrane implanted with Huh7 cells. Compound 6 may be a promising candidate targeting hepatocellular carcinoma with low toxic side effects on normal cells.

ASN007 is a selective ERK1/2 inhibitor with preferential activity against RAS-and RAF-mutant tumors

Inhibition of the extracellular signal-regulated kinases ERK1 and ERK2 (ERK1/2) offers a promising therapeutic strategy in cancers harboring activated RAS/RAF/MEK/ERK signaling pathways. Here, we describe an orally bioavailable and selective ERK1/2 inhibitor, ASN007, currently in clinical development for the treatment of cancer. In preclinical studies, ASN007 shows strong antiproliferative activity in tumors harboring mutations in BRAF and RAS (KRAS, NRAS, and HRAS). ASN007 demonstrates activity in a BRAFV600E mutant melanoma tumor model that is resistant to BRAF and MEK inhibitors. The PI3K inhibitor copanlisib enhances the antiproliferative activity of ASN007 both in vitro and in vivo due to dual inhibition of RAS/MAPK and PI3K survival pathways. Our data provide a rationale for evaluating ASN007 in RAS/RAF-driven tumors as well as a mechanistic basis for combining ASN007 with PI3K inhibitors.

In-transit metastatic cutaneous melanoma: current management and future directions

Management of in-transit melanoma encompasses a variety of possible treatment pathways and modalities. Depending on the location of disease, number of lesions, burden of disease and patient preference and characteristics, some treatments may be more beneficial than others. After full body radiographic staging is performed to rule out metastatic disease, curative therapy may be performed through surgical excision, intraarterial regional perfusion and infusion therapies, intralesional injections, systemic therapies or various combinations of any of these. While wide excision is limited in indication to superficial lesions that are few in number, the other listed therapies may be effective in treating unresectable disease. Where intraarterial perfusion based therapies have been shown to successfully treat extremity disease, injectable therapies can be used in lesions of the head and neck. Although systemic therapies for in-transit melanoma have limited specific data to support their primary use for in-transit disease, there are patients who may not be eligible for any of the other options, and current clinical trials are exploring the use of concurrent and sequential use of regional and systemic therapies with early results suggesting a synergistic benefit for oncologic response and outcomes.

mTOR signaling regulates gastric epithelial progenitor homeostasis and gastric tumorigenesis via MEK1-ERKs and BMP-Smad1 pathways

mTOR, the sensor of nutrients and growth factors, has important roles in tissue homeostasis and tumorigenesis. However, how mTOR controls gastric epithelial cell turnover and gastric cancer development, a leading malignancy, remains poorly understood. Here, we provide genetic evidence that mTOR activation promotes proliferation and inhibits differentiation of Lgr5⁺ gastric epithelial progenitors (GEPs) in gastric homeostasis and tumorigenesis. mTOR signaling increases MEK1 and Smad1 expression and enhances activation of MEK1-ERKs and BMP-Smad1 pathways, respectively, in GEPs and gastric tumors. Mek1 deletion or inhibition rescues hyperproliferation, whereas Bmpr1a ablation or inhibition rescues differentiation defects of Tsc1^-/- GEPs. Tsc1 deficiency in Lgr5⁺ GEPs accelerates gastric tumor initiation and development, which require MEK1-ERKs for hyperplasia and BMP-Smad1 for differentiation suppression. These findings reveal how mTOR signaling controls Lgr5⁺ GEP homeostasis and cancerization and suggest that ERKs and Smad1 signaling can be safely targeted to substitute mTOR inhibitors in gastric cancer therapy.

Mutational profile of skin lesions in hepatocellular carcinoma patients under tyrosine kinase inhibition: a repercussion of a wide-spectrum activity

BACKGROUND/AIM

Dermatological adverse events (DAE) in hepatocellular carcinoma (HCC) patients treated with sorafenib predicts better outcome. Some turn into skin lesions (SL) requiring pathology examination. We describe incidence, characteristics and molecular profile of SL in HCC patients treated with sorafenib.

MATERIALS AND METHODS

SL were prospectively collected in 311 HCC patients who started sorafenib. SL from sorafenib cohort were compared to those from a control patient group selected to match SL type and demographics. HRAS, KRAS and BRAF mutations were analyzed by CAST-PCR, mutated p53 and MAPK pathway activation by immunohistochemistry and immune infiltration by hematoxylin-eosin staining.

RESULTS

Eighty-eight out of 311 patients developed DAE and 7.4% SL required histological assessment. Most frequent lesions were keratoacanthomas (n = 4), squamous-cell carcinomas (SCC)(n = 5), basal-cell carcinomas (BCC)(n = 3) and seborrheic keratosis (n = 5). HRAS and KRAS mutations were detected in 4 SL, while no mutations showed in control SL. Nuclear pERK immunostaining was identified in 33.3% of cases versus 5.3% of controls. Most SL (90%) from patients with DAE were proliferative with intense immune infiltration (73%).

CONCLUSIONS

The onset of SL and their molecular profile did not impact negatively on patient's prognosis, but intense proliferation of SL may reflect compensatory activation of MAPK pathway and warrants their close monitoring.

Inhibition of BRAF and ERK1/2 has synergistic effects on thyroid cancer growth in vitro and in vivo

Mutations in the BRAF gene are highly prevalent in thyroid cancer. However, the response rate of thyroid tumors to BRAF-directed therapies has been mixed. Increasingly, combination therapies inhibiting the MAPK pathway at multiple nodes have shown promise. Recently developed ERK1/2 inhibitors are of interest for use in combination therapies as they have the advantage of inhibiting the most downstream node of the MAPK pathway, therefore preventing pathway reactivation. Here, we examined the effect of combined BRAF inhibition (dabrafenib) and ERK1/2 inhibition (SCH772984) on the growth and survival of a panel of BRAF-mutant thyroid cancer cell lines using in vitro and in vivo approaches. We found that resistance due to MAPK pathway reactivation occurs quickly with single-agent BRAF inhibition, but can be prevented with combined BRAF and ERK1/2 inhibition. Combined inhibition also results in synergistic growth inhibition, decreased clonogenic survival, and enhanced induction of apoptosis in a subset of BRAF-mutant thyroid cancer cells. Finally, combined inhibition of BRAF and ERK1/2 results in enhanced inhibition of tumor growth in an anaplastic thyroid cancer in vivo model. These results provide key rationale to pursue combined BRAF and ERK1/2 inhibition as an alternative therapeutic strategy for BRAF-mutant advanced thyroid cancer patients.

Tumour-Agnostic Therapy for Pancreatic Cancer and Biliary Tract Cancer

The prognosis of patients with solid tumours has remarkably improved with the development of molecular-targeted drugs and immune checkpoint inhibitors. However, the improvements in the prognosis of pancreatic cancer and biliary tract cancer is delayed compared to other carcinomas, and the 5-year survival rates of distal-stage disease are approximately 10 and 20%, respectively. However, a comprehensive analysis of tumour cells using The Cancer Genome Atlas (TCGA) project has led to the identification of various driver mutations. Evidently, few mutations exist across organs, and basket trials targeting driver mutations regardless of the primary organ are being actively conducted. Such basket trials not only focus on the gate keeper-type oncogene mutations, such as HER2 and BRAF, but also focus on the caretaker-type tumour suppressor genes, such as BRCA1/2, mismatch repair-related genes, which cause hereditary cancer syndrome. As oncogene panel testing is a vital approach in routine practice, clinicians should devise a strategy for improved understanding of the cancer genome. Here, the gene mutation profiles of pancreatic cancer and biliary tract cancer have been outlined and the current status of tumour-agnostic therapy in these cancers has been reported.

IL-36γ drives skin toxicity induced by EGFR/MEK inhibition and commensal Cutibacterium acnes

Epidermal growth factor receptor (EGFR) and MEK inhibitors (EGFRi/MEKi) are beneficial for the treatment of solid cancers but are frequently associated with severe therapy-limiting acneiform skin toxicities. The underlying molecular mechanisms are poorly understood. Using gene expression profiling we identified IL-36γ and IL-8 as candidate drivers of EGFRi/MEKi skin toxicity. We provide molecular and translational evidence that EGFRi/MEKi in concert with the skin commensal bacterium Cutibacterium acnes act synergistically to induce IL-36γ in keratinocytes and subsequently IL-8, leading to cutaneous neutrophilia. IL-36γ expression was the combined result of C. acnes–induced NF-κB activation and EGFRi/MEKi–mediated expression of the transcription factor Krüppel-like factor 4 (KLF4), due to the presence of both NF-κB and KLF4 binding sites in the human IL-36γ gene promoter. EGFRi/MEKi increased KLF4 expression by blockade of the EGFR/MEK/ERK pathway. These results provide an insight into understanding the pathological mechanism of the acneiform skin toxicities induced by EGFRi/MEKi and identify IL-36γ and the transcription factor KLF4 as potential therapeutic targets.

A CRAF/glutathione-S-transferase P1 complex sustains autocrine growth of cancers with KRAS and BRAF mutations

A strategy to overcome therapeutic obstacles of mKRAS and mBRAF cancers is devised based on the finding, here, that the RAF/MEK/ERK cascade is by-passed by an autocrine signal loop established by interaction of CRAF with GSTP1. The interaction evokes stabilization of CRAF from proteosomal degradation and facilitation of RAF-dimer formation. Thus, blocking CRAF/GSTP1 interactions should generate additive antiproliferative effects.

The Ras/RAF/MEK/ERK pathway is an essential signaling cascade for various refractory cancers, such as those with mutant KRAS (mKRAS) and BRAF (mBRAF). However, there are unsolved ambiguities underlying mechanisms for this growth signaling thereby creating therapeutic complications. This study shows that a vital component of the pathway CRAF is directly impacted by an end product of the cascade, glutathione transferases (GST) P1 (GSTP1), driving a previously unrecognized autocrine cycle that sustains proliferation of mKRAS and mBRAF cancer cells, independent of oncogenic stimuli. The CRAF interaction with GSTP1 occurs at its N-terminal regulatory domain, CR1 motif, resulting in its stabilization, enhanced dimerization, and augmented catalytic activity. Consistent with the autocrine cycle scheme, silencing GSTP1 brought about significant suppression of proliferation of mKRAS and mBRAF cells in vitro and suppressed tumorigenesis of the xenografted mKRAS tumor in vivo. GSTP1 knockout mice showed significantly impaired carcinogenesis of mKRAS colon cancer. Consequently, hindering the autocrine loop by targeting CRAF/GSTP1 interactions should provide innovative therapeutic modalities for these cancers.

Current State of Target Treatment in BRAF Mutated Melanoma

Incidence of melanoma has been constantly growing during the last decades. Although most of the new diagnoses are represented by thin melanomas, the number of melanoma-related deaths in 2018 was 60,712 worldwide (Global Cancer Observatory, 2019). Until 2011, no systemic therapy showed to improve survival in patients with advanced or metastatic melanoma. At that time, standard of care was chemotherapy, with very limited results. The identification of BRAF V600 mutation, and the subsequent introduction of BRAF targeting drugs, radically changed the clinical practice and dramatically improved outcomes. In this review, we will retrace the development of molecular-target drugs and the current therapeutic scenario for patients with BRAF mutated melanoma, from the introduction of BRAF inhibitors as single agents to modern clinical practice. We will also discuss the resistance mechanisms identified so far, and the future therapeutic perspectives in BRAF mutated melanoma.

Applying support-vector machine learning algorithms toward predicting host-guest interactions with cucurbit[7]uril

Machine learning is a valuable tool in the development of chemical technologies but its applications into supramolecular chemistry have been limited. Here, the utility of kernel-based support vector machine learning using density functional theory calculations as training data is evaluated when used to predict equilibrium binding coefficients of small molecules with cucurbit[7]uril (CB[7]). We find that utilising SVMs may confer some predictive ability. This algorithm was then used to predict the binding of drugs TAK-580 and selumetinib. The algorithm did predict strong binding for TAK-580 and poor binding for selumetinib, and these results were experimentally validated. It was discovered that the larger homologue cucurbit[8]uril (CB[8]) is partial to selumetinib, suggesting an opportunity for tunable release by introducing different concentrations of CB[7] or CB[8] into a hydrogel depot. We qualitatively demonstrated that these drugs may have utility in combination against gliomas. Finally, mass transfer simulations show CB[7] can independently tune the release of TAK-580 without affecting selumetinib. This work gives specific evidence that a machine learning approach to recognition of small molecules by macrocycles has merit and reinforces the view that machine learning may prove valuable in the development of drug delivery systems and supramolecular chemistry more broadly.

Bintrafusp Alfa, a Bifunctional Fusion Protein Targeting TGF-β and PD-L1, in Second-Line Treatment of Patients With NSCLC: Results From an Expansion Cohort of a Phase 1 Trial

INTRODUCTION

The safety and efficacy of bintrafusp alfa, a first-in-class bifunctional fusion protein composed of the extracellular domain of the transforming growth factor β (TGF-β) receptor II (a TGF-β "trap") fused to a human immunoglobulin G1 antibody blocking programmed death-ligand 1 (PD-L1), was evaluated in patients with advanced NSCLC.

METHODS

This expansion cohort of NCT02517398, an ongoing, phase 1, open-label trial, includes 80 patients with advanced NSCLC that progressed after platinum doublet therapy or after platinum-based adjuvant or neoadjuvant treatment and those who also have not received previous immunotherapy. Patients were randomized at a one-to-one ratio to receive either bintrafusp alfa 500 mg or the recommended phase 2 dosage of 1200 mg every 2 weeks. The primary end point was the best overall response (by Response Evaluation Criteria in Solid Tumors 1.1 as adjudicated by independent review committee) and was assessed by the objective response rate (ORR).

RESULTS

A total of 80 patients were randomized to receive bintrafusp alfa 500 or 1200 mg (n = 40 each). Median follow-up was 51.9 weeks (IQR, 19.6-74.0). The ORR in all patients was 21.3% (17 of 80). The ORR was 17.5% (seven of 40) and 25.0% (10 of 40) for the 500 mg dose and the 1200 mg dose (recommended phase 2 dose), respectively. At the 1200 mg dose, patients with PD-L1-positive and PD-L1-high (≥80% expression on tumor cells) had ORRs of 36.0% (10 of 27) and 85.7% (six of seven), respectively. Treatment-related adverse events occurred in 55 of the 80 patients (69%) and were graded as greater than or equal to 3 in 23 of the 80 patients (29%). Of the 80 patients, eight (10%) had a treatment-related adverse event that led to treatment discontinuation; no treatment-related deaths occurred.

CONCLUSIONS

Bintrafusp alfa had encouraging efficacy and manageable tolerability in patients with NSCLC previously treated with platinum.

Optimal treatment strategy for metastatic melanoma patients harboring BRAF-V600 mutations

BRAF-V600 mutations occur in approximately 50% of patients with metastatic melanoma. Immune-checkpoint inhibitors and targeted therapies are both active as first-line treatments in these patients regardless of their mechanisms of action and toxicities. However, an upfront therapeutic strategy is still controversial. In fact, waiting for results of ongoing clinical trials and for new biomarkers, clinicians should base their decision on the clinical characteristics of the patient and on the biological aspects of the tumor. This review provides an overview on BRAF-V600 mutations in melanoma and will discuss their prognostic and clinical significance. Moreover, it will suggest a therapeutic algorithm that can drive therapeutic choice in a first-line setting for BRAF-V600 mutant melanoma patients.

Cutaneous Squamous Cell Carcinoma: From Biology to Therapy

Cutaneous squamous cell carcinoma (CSCC) is the second most frequent cancer in humans and its incidence continues to rise. Although CSCC usually display a benign clinical behavior, it can be both locally invasive and metastatic. The signaling pathways involved in CSCC development have given rise to targetable molecules in recent decades. In addition, the high mutational burden and increased risk of CSCC in patients under immunosuppression were part of the rationale for developing the immunotherapy for CSCC that has changed the therapeutic landscape. This review focuses on the molecular basis of CSCC and the current biology-based approaches of targeted therapies and immune checkpoint inhibitors. Another purpose of this review is to explore the landscape of drugs that may induce or contribute to the development of CSCC. Beginning with the pathogenetic basis of these drug-induced CSCCs, we move on to consider potential therapeutic opportunities for overcoming this adverse effect.

The rise of T-type channels in melanoma progression and chemotherapeutic resistance

Hyperactivation of the Mitogen Activated Protein Kinase (MAPK) pathway is prevalent in melanoma, principally due to mutations in the BRAF and NRAS genes. MAPK inhibitors are effective only short-term, and recurrence occurs due to functional redundancies or intertwined pathways. The remodeling of Ca²⁺ signaling is also common in melanoma cells, partly through the increased expression of T-type channels (TTCCs). Here we summarize current knowledge about the prognostic value and molecular targeting of TTCCs. Furthermore, we discuss recent evidence pointing to TTCCs as molecular switches for melanoma chemoresistance, which set the grounds for novel combined therapies against the advanced disease.

Dual BRAF/MEK blockade restores CNS responses in BRAF-mutant Erdheim-Chester disease patients following BRAF inhibitor monotherapy

Background

Erdheim–Chester disease (ECD), a rare inflammatory myeloid neoplasm, is known to be fundamentally reliant on the constitutive activation of the MAPK signaling pathway in the majority of patients. Consequently, inhibition of the V600E-mutant BRAF kinase has proven to be a safe and efficacious long-term therapeutic strategy for BRAF-mutant ECD patients. Nevertheless, in a subset of patients with CNS disease, the efficacy of long-term treatment may diminish, facilitating suboptimal responses or disease progression.

Methods

We retrospectively describe 3 BRAF-mutant ECD patients whose treatment with Vemurafenib was upgraded to Vemurafenib/Cobimetinib due to either disease progression, insufficient response, or unacceptable toxicity. CNS response to therapy was evaluated using magnetic resonance imaging (MRI) and extra-cranial disease was monitored using ¹⁸F-fludeoxyglucose positron emission tomography/computed tomography (PET/CT).

Results

Three patients with a mean age of 52.6 years were treated with Vemurafenib for a mean duration of 26.6 months (range: 6–52). Monotherapies were upgraded to Vemurafenib/Cobimetinib dual therapy. The combination therapy was administered for a mean duration of 21 months (range: 19–23). All patients exhibited clinical and neurological improvement. Regression of lesions on MRI was noted in 2 patients. Both patients characterized by a PET-avid disease responded to the biological treatment regimen with complete metabolic remissions.

Conclusion

Dual inhibition of BRAF and downstream MEK may be a safe and effective therapeutic strategy for BRAF-mutant ECD patients for whom BRAF inhibitor therapy proved insufficient and as such appropriate for the long-term management of CNS disease in ECD.

Tracking extracellular vesicle phenotypic changes enables treatment monitoring in melanoma

Monitoring targeted therapy in real time for cancer patients could provide vital information about the development of drug resistance and improve therapeutic outcomes. Extracellular vesicles (EVs) have recently emerged as a promising cancer biomarker, and EV phenotyping shows high potential for monitoring treatment responses. Here, we demonstrate the feasibility of monitoring patient treatment responses based on the plasma EV phenotypic evolution using a multiplex EV phenotype analyzer chip (EPAC). EPAC incorporates the nanomixing-enhanced microchip and the multiplex surface-enhanced Raman scattering (SERS) nanotag system for direct EV phenotyping without EV enrichment. In a preclinical model, we observe the EV phenotypic heterogeneity and different phenotypic responses to the treatment. Furthermore, we successfully detect cancer-specific EV phenotypes from melanoma patient plasma. We longitudinally monitor the EV phenotypic evolution of eight melanoma patients receiving targeted therapy and find specific EV profiles involved in the development of drug resistance, reflecting the potential of EV phenotyping for monitoring treatment responses.

Considering adjuvant therapy for stage II melanoma

Melanoma is among the few cancers that demonstrate an increasing incidence over time. Simultaneously, this trend has been marked by an epidemiologic shift to earlier stage at diagnosis. Before 2011, treatment options were limited for patients with metastatic disease, and the median overall survival was less than 1 year. Since then, the field of melanoma therapeutics has undergone major changes. The use of anti–CTLA‐4 and anti‐PD1 immune checkpoint inhibitors and combination BRAF/MEK inhibitors for patients with BRAF V600 mutations has significantly extended survival and allowed some patients to remain in durable disease remission off therapy. It has now been confirmed that these classes of agents have a benefit for patients with stage III melanoma after surgical resection, and anti‐PD1 and BRAF/MEK inhibitors are standards of care in this setting. Some patients with stage II disease (lymph node‐negative; American Joint Committee on Cancer stage IIB and IIC) have worse melanoma‐specific survival relative to some patients with stage III disease. Given these results, expanding the population of patients who are considered for adjuvant therapy to include those with stage II melanoma has become a priority, and randomized phase 3 clinical trials are underway. Moving into the future, the validation of patient risk‐stratification and treatment‐benefit prediction models will be important to improve the number needed to treat and limit exposure to toxicity in the large population of patients with early stage melanoma.

Adjuvant therapy has improved outcomes in patients with stage III melanoma and is being explored in those with stage II melanoma. Stage III data as well as risk‐stratification tools and clinical considerations for the lymph node‐negative population are reviewed.

Targeting AXL and the DNA Damage Response Pathway as a Novel Therapeutic Strategy in Melanoma

Receptor tyrosine kinase AXL is found upregulated in various types of cancer, including melanoma, and correlates with an aggressive cancer phenotype, inducing cell proliferation and epithelial-to-mesenchymal transition. In addition, AXL has recently been linked to chemotherapy resistance, and inhibition of AXL is found to increase DNA damage and reduce expression of DNA repair proteins. In light of this, we aimed to investigate whether targeting AXL together with DNA damage response proteins would be therapeutically beneficial. Using melanoma cell lines, we observed that combined reduction of AXL and CHK1/CHK2 signaling decreased proliferation, deregulated cell-cycle progression, increased apoptosis, and reduced expression of DNA damage response proteins. Enhanced therapeutic effect of combined treatment, as compared with mono-treatment, was further observed in a patient-derived xenograft model and, of particular interest, when applying a three-dimensional ex vivo spheroid drug sensitivity assay on tumor cells harvested directly from 27 patients with melanoma lymph node metastases. Together, these results indicate that targeting AXL together with the DNA damage response pathway could be a promising treatment strategy in melanoma, and that further investigations in patient groups lacking treatment alternatives should be pursued.

Personalized and targeted mutational analysis of multiple second primary melanomas under kinase inhibitors

BACKGROUND

Second primary melanomas (SPMs) are new developed primary melanomas occurring in a subset of patients affected by BRAF-mutated metastatic melanoma during treatment with BRAF-inhibitors. A drug-induced paradoxical activation of mitogen-activated protein kinase (MAPK) signaling pathway in BRAF-wild type/RAS-mutated cells have been proposed as a possible molecular mechanism but data on the mutational status of SPMs are lacking. In order to better understand genetic alterations affecting the biological mechanism of SPMs, we performed a personalized and targeted next-generation sequencing analysis of a patient affected by metastatic melanoma who developed multiple SPMs during treatment with encorafenib (LGX818).

METHODS

Using a cancer panel of 50 genes for solid tumors enriched with a custom panel of 10 genes specifically involved in melanoma pathogenesis, we analyzed the primary melanoma, two SPMs, one benign compound nevus and the normal DNA extracted from blood lymphocytes of the patient.

RESULTS

We identified HRAS Q61 somatic mutation in one SPM developed in a pre-existing nevus. In the primary melanoma, besides the BRAF mutation, we identified the clinically actionable IDH1 R132C somatic mutation. Both SPMs were BRAF wild type. The patient harbors the recently recognized pathogenetic germline variant KDR Q472. We observed that mutations detected in tumor samples involving genes related to melanoma pathogenesis (TP53, PIK3CA, FGFR3, ATF1, KIT, HRAS and MAP2K2) were present in heterozygosis in the germline status of the patient.

CONCLUSIONS

Our results support the paradoxical mechanism of MAPK pathway for SPMs under BRAF inhibitors. Moreover, they suggest that targeted mutational assessment based on matching somatic and germline analysis represent a promising approach to detect the neoplastic landscape of the tumor and to identify most accurate treatment in metastatic melanoma patient.

The role of polo-like kinase 3 in the response of BRAF-mutant cells to targeted anticancer therapies

The activation of oncogenic mitogen-activated protein kinase cascade via mutations in BRAF is often observed in human melanomas. Targeted inhibitors of BRAF (BRAFi), alone or as a part of a combination therapy, offer a significant benefit to such patients. Unfortunately, some cases are initially nonresponsive to these drugs, while others become refractory in the course of treatment, underscoring the need to understand and mitigate the underlying resistance mechanisms. We report that interference with polo-like kinase 3 (PLK3) reduces the tolerance of BRAF-mutant melanoma cells to BRAFi, while increased PLK3 expression has the opposite effect. Accordingly, PLK3 expression correlates with tolerance to BRAFi in a panel of BRAF-mutant cell lines and is elevated in a subset of recurring BRAFi-resistant melanomas. In PLK3-expressing cells, R406, a kinase inhibitor whose targets include PLK3, recapitulates the sensitizing effects of genetic PLK3 inhibitors. The findings support a role for PLK3 as a predictor of BRAFi efficacy and suggest suppression of PLK3 as a way to improve the efficacy of targeted therapy.