Pan-RAF and MEK vertical inhibition enhances therapeutic response in non-V600 BRAF mutant cells

Development of Personalized Strategies for Precisely Battling Malignant Melanoma

Melanoma is the most severe and fatal form of skin cancer, resulting from multiple gene mutations with high intra-tumor and inter-tumor molecular heterogeneity. Treatment options for patients whose disease has progressed beyond the ability for surgical resection rely on currently accepted standard therapies, notably immune checkpoint inhibitors and targeted therapies. Acquired resistance to these therapies and treatment-associated toxicity necessitate exploring novel strategies, especially those that can be personalized for specific patients and/or populations. Here, we review the current landscape and progress of standard therapies and explore what personalized oncology techniques may entail in the scope of melanoma. Our purpose is to provide an up-to-date summary of the tools at our disposal that work to circumvent the common barriers faced when battling melanoma.

Novel RAF-directed approaches to overcome current clinical limits and block the RAS/RAF node

Mutations in the RAS-RAF-MEK-ERK pathway are frequent alterations in cancer and RASopathies, and while RAS oncogene activation alone affects 19% of all patients and accounts for approximately 3.4 million new cases every year, less frequent alterations in the cascade's downstream effectors are also involved in cancer etiology. RAS proteins initiate the signaling cascade by promoting the dimerization of RAF kinases, which can act as oncoproteins as well: BRAFV600E is the most common oncogenic driver, mutated in the 8% of all malignancies. Research in this field led to the development of drugs that target the BRAFV600-like mutations (Class I), which are now utilized in clinics, but cause paradoxical activation of the pathway and resistance development. Furthermore, they are ineffective against non-BRAFV600E malignancies that dimerize and could be either RTK/RAS independent or dependent (Class II and III, respectively), which are still lacking an effective treatment. This review discusses the recent advances in anti-RAF therapies, including paradox breakers, dimer-inhibitors, immunotherapies, and other novel approaches, critically evaluating their efficacy in overcoming the therapeutic limitations, and their putative role in blocking the RAS pathway.

Supramolecular Biomaterials for Cancer Immunotherapy

Cancer immunotherapy has achieved tremendous successful clinical results and obtained historic victories in tumor treatments. However, great limitations associated with feeble immune responses and serious adverse effects still cannot be neglected due to the complicated multifactorial etiology and pathologic microenvironment in tumors. The rapid development of nanomedical science and material science has facilitated the advanced progress of engineering biomaterials to tackle critical issues. The supramolecular biomaterials with flexible and modular structures have exhibited unparalleled advantages of high cargo-loading efficiency, excellent biocompatibility, and diversiform immunomodulatory activity, thereby providing a powerful weapon for cancer immunotherapy. In past decades, supramolecular biomaterials were extensively explored as versatile delivery platforms for immunotherapeutic agents or designed to interact with the key moleculars in immune system in a precise and controllable manner. In this review, we focused on the crucial role of supramolecular biomaterials in the modulation of pivotal steps during tumor immunotherapy, including antigen delivery and presentation, T lymphocyte activation, tumor-associated macrophage elimination and repolarization, and myeloid-derived suppressor cell depletion. Based on extensive research, we explored the current limitations and development prospects of supramolecular biomaterials in cancer immunotherapy.

The future of targeted kinase inhibitors in melanoma

Melanoma is a cancer of the pigment-producing cells of the body and its incidence is rising. Targeted inhibitors that act against kinases in the MAPK pathway are approved for BRAF-mutant metastatic cutaneous melanoma and increase patients' survival. Response to these therapies is limited by drug resistance and is less durable than with immune checkpoint inhibition. Conversely, rare melanoma subtypes have few therapeutic options for advanced disease and MAPK pathway targeting agents show minimal anti-tumor effects. Nevertheless, there is a future for targeted kinase inhibitors in melanoma: in new applications such as adjuvant or neoadjuvant therapy and in novel combinations with immunotherapies or other targeted therapies. Pre-clinical studies continue to identify tumor dependencies and their corresponding actionable drug targets, paving the way for rational targeted kinase inhibitor combinations as a personalized medicine approach for melanoma.

Re-establishing the comprehension of phytomedicine and nanomedicine in inflammation-mediated cancer signaling

Recent mounting evidence has revealed extensive genetic heterogeneity within tumors that drive phenotypic variation affecting key cancer pathways, making cancer treatment extremely challenging. Diverse cancer types display resistance to treatment and show patterns of relapse following therapy. Therefore, efforts are required to address tumor heterogeneity by developing a broad-spectrum therapeutic approach that combines targeted therapies. Inflammation has been progressively documented as a vital factor in tumor advancement and has consequences in epigenetic variations that support tumor instigation, encouraging all the tumorigenesis phases. Increased DNA damage, disrupted DNA repair mechanisms, cellular proliferation, apoptosis, angiogenesis, and its incursion are a few pro-cancerous outcomes of chronic inflammation. A clear understanding of the cellular and molecular signaling mechanisms of tumor-endorsing inflammation is necessary for further expansion of anti-cancer therapeutics targeting the crosstalk between tumor development and inflammatory processes. Multiple inflammatory signaling pathways, such as the NF-κB signaling pathway, JAK-STAT signaling pathway, MAPK signaling, PI3K/AKT/mTOR signaling, Wnt signaling cascade, and TGF-β/Smad signaling, have been found to regulate inflammation, which can be modulated using various factors such as small molecule inhibitors, phytochemicals, recombinant cytokines, and nanoparticles in conjugation to phytochemicals to treat cancer. Researchers have identified multiple targets to specifically alter inflammation in cancer therapy to restrict malignant progression and improve the efficacy of cancer therapy. siRNA-and shRNA-loaded nanoparticles have been observed to downregulate STAT3 signaling pathways and have been employed in studies to target tumor malignancies. This review highlights the pathways involved in the interaction between tumor advancement and inflammatory progression, along with the novel approaches of nanotechnology-based drug delivery systems currently used to target inflammatory signaling pathways to combat cancer.

Experiments from unfinished Registered Reports in the Reproducibility Project: Cancer Biology

As part of the Reproducibility Project: Cancer Biology, we published Registered Reports that described how we intended to replicate selected experiments from 29 high-impact preclinical cancer biology papers published between 2010 and 2012. Replication experiments were completed and Replication Studies reporting the results were submitted for 18 papers, of which 17 were accepted and published by eLife with the rejected paper posted as a preprint. Here, we report the status and outcomes obtained for the remaining 11 papers. Four papers initiated experimental work but were stopped without any experimental outcomes. Two papers resulted in incomplete outcomes due to unanticipated challenges when conducting the experiments. For the remaining five papers only some of the experiments were completed with the other experiments incomplete due to mundane technical or unanticipated methodological challenges. The experiments from these papers, along with the other experiments attempted as part of the Reproducibility Project: Cancer Biology, provides evidence about the challenges of repeating preclinical cancer biology experiments and the replicability of the completed experiments.

pH-Sensitive Molecular-Switch-Containing Polymer Nanoparticle for Breast Cancer Therapy with Ferritinophagy-Cascade Ferroptosis and Tumor Immune Activation

Ferritin internalized into tumor cells is degraded and releases iron ions via ferritinophagy. Iron ions participate in Fenton reaction to produce reactive oxygen species for lipid peroxidation and ferroptosis. Inhibition of indoleamine-2,3-dioxygenase (IDO) decreases tryptophan elimination to induce T cells activation for tumor immunosuppression relief. The active tumor targeting nanoparticles containing ferritin and a pH-sensitive molecular-switch (FPBC@SN) are developed to utilize ferritinophagy-cascade ferroptosis and tumor immunity activation for cancer therapy. FPBC@SN disintegrates in acidic cytoplasm and releases sorafenib (SRF) and IDO inhibitor (NLG919). SRF upregulates nuclear receptor coactivator 4 (NCOA4) to induce ferritin and endogenous iron pool degradation by ferritinophagy, then obtained iron ions participate in the Fenton reaction to produce lipid peroxide (LPO). Meanwhile, SRF blocks glutathione synthesis to downregulate glutathione peroxidase 4 (GPX4) which can scavenge LPO as a different pathway from ferritinophagy to promote ferroptosis in tumor cells. NLG919 inhibits IDO to reduce tryptophan metabolism, so immunity in tumors is aroused to anti-tumor. In vitro and in vivo experiments prove FPBC@SN inhibits tumor cell growth and metastasis, indicating the potential of FPBC@SN for breast cancer therapy based on the combination of ferritinophagy-cascade ferroptosis and tumor immunity activation.

Small molecules in targeted cancer therapy: advances, challenges, and future perspectives

Due to the advantages in efficacy and safety compared with traditional chemotherapy drugs, targeted therapeutic drugs have become mainstream cancer treatments. Since the first tyrosine kinase inhibitor imatinib was approved to enter the market by the US Food and Drug Administration (FDA) in 2001, an increasing number of small-molecule targeted drugs have been developed for the treatment of malignancies. By December 2020, 89 small-molecule targeted antitumor drugs have been approved by the US FDA and the National Medical Products Administration (NMPA) of China. Despite great progress, small-molecule targeted anti-cancer drugs still face many challenges, such as a low response rate and drug resistance. To better promote the development of targeted anti-cancer drugs, we conducted a comprehensive review of small-molecule targeted anti-cancer drugs according to the target classification. We present all the approved drugs as well as important drug candidates in clinical trials for each target, discuss the current challenges, and provide insights and perspectives for the research and development of anti-cancer drugs.

Horizontal Combination of MEK and PI3K/mTOR Inhibition in BRAF Mutant Tumor Cells with or without Concomitant PI3K Pathway Mutations

The RAS/RAF and PI3K/Akt pathways play a key regulatory role in cancer and are often hit by oncogenic mutations. Despite molecular targeting, the long-term success of monotherapy is often hampered by de novo or acquired resistance. In the case of concurrent mutations in both pathways, horizontal combination could be a reasonable approach. In our study, we investigated the MEK inhibitor selumetinib and PI3K/mTOR dual inhibitor BEZ235 alone and in combination in BRAF-only mutant and BRAF + PI3K/PTEN double mutant cancer cells using short- and long-term 2D viability assays, spheroid assays, and immunoblots. In the 2D assays, selumetinib was more effective on BRAF-only mutant lines when compared to BRAF + PI3K/PTEN double mutants. Furthermore, combination therapy had an additive effect in most of the lines while synergism was observed in two of the double mutants. Importantly, in the SW1417 BRAF + PI3K double mutant cells, synergism was also confirmed in the spheroid and in the in vivo model. Mechanistically, p-Akt level decreased only in the SW1417 cell line after combination treatment. In conclusion, the presence of concurrent mutations alone did not predict a stronger response to combination treatment. Therefore, additional investigations are warranted to identify predictive factors that can select patients who can benefit from the horizontal combinational inhibition of these two pathways.

Dual inhibition of CSF1R and MAPK pathways using supramolecular nanoparticles enhances macrophage immunotherapy

Among the numerous immune interactions, or lack-thereof, that occur during cancer progression, tumor-associated macrophages (TAMs) - cancer cell interactions have been shown to play an important role in modulating the tumor-microenvironment to an immune suppressive mode, promoting accelerated tumor growth, survival and metastatic spread. TAMs are predominantly polarized to a pro-tumorigenic M2-phenotype through macrophage colony stimulating factor 1 (MCSF) cytokines that bind to the colony-stimulating factor 1 receptor (CSF1R), a class III receptor tyrosine kinase. This MCSF-CSF1R interaction results in autophosphorylation of CSF1R and subsequent phosphorylation and activation of downstream signaling pathways including mitogen-activated protein kinase (MAPK) pathway leading to proliferation, survival and functional activity of M2 TAMs. Therapeutic inhibition of CSF1R and MAPK signaling could effectively re-polarize M2 macrophages to an anti-tumorigenic M1 phenotype; however, this is challenging. In this study, we demonstrate that concurrent and sustained inhibition of the CSF1R and MAPK signaling pathways using dual-kinase inhibitor-loaded supramolecular nanoparticles (DSNs) enhance repolarization of pro-tumorigenic M2 macrophages to the anti-tumorigenic M1 phenotype. The supramolecular nanoparticles exhibited physical stability of over 7 days during storage conditions at 4 °C and over 24 h in human serum, released the inhibitors in a sustained manner and showed significantly higher internalization and accumulation of inhibitors in the M2 macrophages even at longer time points. When tested in a highly aggressive 4T1 breast cancer model, the supramolecular nanoparticles accumulated in TAMs at a significantly higher concentration, increased M1-like phenotype at significantly higher proportion and improved anti-tumor efficacy as compared to combination of single-inhibitor nanoparticles or the small molecule inhibitors. Our data suggests that concurrent, vertical inhibition of multiple intracellular kinase signaling pathways is important for repolarization of M2 macrophages to M1 phenotype, and by utilizing dual-inhibitor loaded supramolecular nanoparticles, further increase the ability to produce more M1 macrophages as compared to M2 macrophages in the tumor microenvironment. This results in enhanced tumor growth inhibition and reduced toxicity. Therefore, vertical, co-inhibition of CSF1R and downstream signaling pathways like MAPK could be a promising macrophage immunotherapy strategy for aggressive cancers.

Histiocytic Sarcoma Following B-Lymphoblastic Leukemia/Lymphoma

OBJECTIVES

Rare cases of clonally related histiocytic sarcoma (HS) following B-lymphoblastic leukemia/lymphoma (B-ALL/LBL) have been reported to date.

METHODS

We present a patient with HS, which appeared as a breast mass 12 months after the initial diagnosis of B-ALL.

RESULTS

Both HS and the B-ALL shared IGH-MYC and IGK gene rearrangements. Next-generation sequencing and whole-exome sequencing (WES) studies detected 35 common mutations, as well as mutations unique to B-ALL (16) and HS (15), including BRAF D594G. The patient achieved complete remission of B-ALL, but HS failed to respond to many cycles of intensive chemotherapy regimens. A partial response was achieved with sorafenib, a BRAF-targeted therapy.

CONCLUSIONS

To our knowledge, this is the first study to demonstrate by WES that clonally related B-ALL and HS arise through divergent evolution from a common precursor. We present our findings together with a discussion of the previously reported cases of HS in patients with B-ALL.

STAT3 inhibitor sensitized KRAS-mutant lung cancers to RAF inhibitor by activating MEK/ERK signaling pathway

KRAS is frequently mutated in patients with lung cancers, resulting in low survival rates. Inhibiting the downstream pathways of KRAS seems to be a feasible strategy to target KRAS-mutant tumors. However, the clinical outcomes only show limited success. Here, we developed a novel strategy by combining RAF (AZ628) and STAT3 (BP-1-102) inhibitors. The results showed that the AZ628 and BP-1-102 combination showed strongly synergistic effects on KRAS(G12D) H838, KRAS(G12S) H292 and KRAS(G12V) H441 cells and significantly enhanced the inhibition of cell proliferation in vitro and tumor growth in vivo by promoting apoptosis compared with one inhibitor alone. For mechanism, AZ628 and BP-1-102 combination markedly abrogated MEK/ERK signaling pathway activation in KRAS-mutant lung cancer cells suggesting the combination of RAF and STAT3 inhibitors is an effective therapy for treating lung cancer cells harboring KRAS mutations. Taken together, the current results indicate that oncogene addiction can be targeted for therapy in lung cancer cells harboring RAS-mutant.

CRAF mutations in lung cancer can be oncogenic and predict sensitivity to combined type II RAF and MEK inhibition

Two out of 41 non-small cell lung cancer patients enrolled in a clinical study were found with a somatic CRAF mutation in their tumor, namely CRAF^P261A and CRAF^P207S. To our knowledge, both mutations are novel in lung cancer and CRAF^P261A has not been previously reported in cancer. Expression of CRAF^P261A in HEK293T cells and BEAS-2B lung epithelial cells led to increased ERK pathway activation in a dimer-dependent manner, accompanied with loss of CRAF phosphorylation at the negative regulatory S259 residue. Moreover, stable expression of CRAF^P261A in mouse embryonic fibroblasts and BEAS-2B cells led to anchorage-independent growth. Consistent with a previous report, we could not observe a gain-of-function with CRAF^P207S. Type II but not type I RAF inhibitors suppressed the CRAF^P261A-induced ERK pathway activity in BEAS-2B cells, and combinatorial treatment with type II RAF inhibitors and a MEK inhibitor led to a stronger ERK pathway inhibition and growth arrest. Our findings suggest that the acquisition of a CRAF^P261A mutation can provide oncogenic properties to cells, and that such cells are sensitive to combined MEK and type II RAF inhibitors. CRAF mutations should be diagnostically and therapeutically explored in lung and perhaps other cancers.