Pilot study of PD-0325901 in previously treated patients with advanced melanoma, breast cancer, and colon cancer. Cancer Chemother Pharmacol. 2011;68:547-552. [PMID: 21516509 DOI: 10.1007/s00280-011-1620-1]

Multiple anti-tumor programs are activated by blocking BAD phosphorylation

The Bcl-2 family member BAD is a candidate disease modulator because it stimulates apoptosis in a cell context basis and inhibits cell migration during normal mammary gland morphogenesis. This activity depends on 3 key regulatory serines (S75, 99, 118) in the unphosphorylated state. Given that developmental programs are often hijacked in cancer, we hypothesized that BAD would impede breast cancer progression. We generated breast cancer mouse models representing loss-of-function or phosphorylation deficient mutations (PyMT-Bad-/- and PyMT-Bad3SA/3SA, respectively). Preventing BAD phosphorylation significantly decreased breast cancer progression and metastasis. The knock-out phenocopied the control PyMT-Bad+/+ suggesting that phosphorylated BAD protein was inert. Thus, the BAD3SA mutation unmasked latent anti-tumor activity. Indeed, transcriptomics showed PyMT-Bad3SA/3SA activated multiple anti-tumor programs including apoptosis, inflammation, cellular differentiation, and diminished cell migration. This anti-tumor effect associated with clinical survival of breast cancer patients whose tumors had high levels of unphosphorylated BAD. Kinase screens identified ERK as the major BAD kinase in breast cells, and ERK inhibition impeded tumoroid invasion. Our data suggest that unphosphorylated BAD modulates anti-tumor pathways that contribute to excellent patient prognosis. Thus, targeting ERK to dephosphorylate BAD may be an exciting therapeutic opportunity in the future.

An immune biomarker associated with EMT serves as a predictor for prognosis and drug response in bladder cancer

BACKGROUND

Bladder cancer (BLCA), which develops from the upper endometrial of the bladder, is the sixth most prevalent cancer across the globe. WDHD1 (WD repeat and HMG-box DNA binding protein 1 gene) directly affects signaling, the cell cycle, and the development of the cell skeleton. Uncertainty surrounds WDHD1's function in BLCA immunity and prognosis, though.

MATERIALS AND METHODS

Using weighed gene co-expression network analysis (WGCNA), initially, we first identified 32 risk factors in genes with differential expression for this investigation. Then, using a variety of bioinformatic techniques and experimental validation, we examined the connections between WDHD1 and BLCA expression, clinical pathological traits, WDHD1-related proteins, upper-skin-intermediate conversion (EMT), immune cell immersion, convergence factors, immune markers, and drug sensitivity.

RESULT

The findings demonstrated that we constructed a 32-gene risk-predicting model where WDHD1 was elevated as a representative gene expression in BLCA and related to a range of clinical traits. Furthermore, high WDHD1 expression was a standalone predictor associated with a worse survival rate. The most commonly recruited cells and their evolutionary patterns were highlighted to better comprehend WDHD1's function in cancer. High WDHD1 expression was associated with many aspects of immunology. Finally, the study found that individuals with high expression of WDHD1 were drug-sensitive to four different broad-spectrum anti-cancer drugs.

CONCLUSION

These results describe dynamic changes in the tumor microenvironment in BLCA and provide evidence for the hypothesis that WDHD1 is a novel biomarker of tumor development. WDHD1 may therefore be a useful target for the detection and management of BLCA.

MEK inhibitors in cancer treatment: structural insights, regulation, recent advances and future perspectives

MEK1/2 are critical components of the RAS-RAF-MEK-ERK or MAPK signalling pathway that regulates a variety of cellular functions including proliferation, survival, and differentiation. In 1997, a lung cancer cell line was first found to have a MEK mutation (encoding MEK2P298L). MEK is involved in various human cancers such as non-small cell lung cancer (NSCLC), spurious melanoma, and pancreatic, colorectal, basal, breast, and liver cancer. To date, 4 MEK inhibitors i.e., trametinib, cobimetinib, selumetinib, and binimetinib have been approved by the FDA and several are under clinical trials. In this review, we have highlighted structural insights into the MEK1/2 proteins, such as the αC-helix, catalytic loop, P-loop, F-helix, hydrophobic pocket, and DFG motif. We have also discussed current issues with all FDA-approved MEK inhibitors or drugs under clinical trials and combination therapies to improve the efficacy of clinical drugs. Finally, this study addressed recent developments on synthetic MEK inhibitors (from their discovery in 1997 to 2022), their unique properties, and their relevance to MEK mutant inhibition.

Toxic neuropathies

PURPOSE OF REVIEW

Immunotherapy has had a significant impact on the treatment of an increasing number of cancers as well as in inflammatory, rheumatological and gastroenterological conditions.Recreational nitrous oxide use is now a global epidemic. Linezolid is now recommended for the treatment of drug-resistant tuberculosis (TB); neuropathy is a significant cause of morbidity.Global warming will result in increasing toxin exposure, such as ciguatera, in previously unaffected areas.

RECENT FINDINGS

With increasing experience, the pathophysiology underlying the neuropathic complications of these drugs has become clear with guidelines now available, for the complications of immune check-point inhibitors and nitrous oxide toxicity. The optimum dose and duration of treatment for resistant TB with regimens, including linezolid, has been ascertained.

SUMMARY

Although neuropathic complications with immunotherapy are relatively rare, it is essential that they are recognized and treated early. Nitrous oxide toxicity should be in the differential diagnosis for all patients, particularly those of younger age, presenting with a neuropathy or myleo-neuropathy. Ciguatera toxicity is under recognized and its geographical spread will increase due to global warming. Further research is necessary on the mechanisms and treatment of both acute and chronic effects, which at present, are only symptomatic.

Optically activated MEK1/2 inhibitors (Opti-MEKi) as potential antimelanoma agents

Mitogen-activated protein kinase kinases 1/2 (MEK1/2) play critical roles in the canonical RAS/RAF/MEK/ERK pathway. Highly selective and potent non-ATP-competitive allosteric MEK1/2 inhibitors have been developed, and three of them were clinically approved for the treatment of BRAFV600 -mutant melanoma. However, the accompanying side effects of the systemically administered MEK1/2 drugs largely constrain their tolerable doses and efficacy. In this study, a series of mirdametinib-based optically activatable MEK1/2 inhibitors (opti-MEKi) were designed and synthesized. A structural-based design led to the discovery of photocaged compounds with dramatically diminished efficacy in vitro, whose activities can be spatiotemporally induced by short durations of irradiation of ultraviolet (365 nm) light. We demonstrated the robust photoactivation of MEK1/2 inhibition and antimelanoma activity in cultured human cells, as well as in a xenograft zebrafish model. Taken together, the modular approach presented herein provides a method for the optical control of MEK1/2 inhibitor activity, and these data support the further development of optically activatable agents for light-mediated antimelanoma phototherapy.

The emerging era of personalized medicine in advanced colorectal cancer

Colorectal cancer (CRC) is a genetically heterogeneous disease with its pathogenesis often driven by varying genetic or epigenetic alterations. This has led to a substantial number of patients developing chemoresistance and treatment failure, resulting in a high mortality rate for advanced disease. Deep molecular analysis has allowed for the discovery of key intestinal signaling pathways which impacts colonic epithelial cell fate, and the integral role of the tumor microenvironment on cancer growth and dissemination. Through transitioning pre-clinical knowledge in research into clinical practice, many potential druggable targets within these pathways have been discovered in the hopes of overcoming the roadblocks encountered by conventional therapies. A personalized approach tailoring treatment according to the histopathological and molecular features of individual tumors can hopefully translate to better patient outcomes, and reduce the rate of recurrence in patients with advanced CRC. Herein, the latest understanding on the molecular science behind CRC tumorigenesis, and the potential treatment targets currently at the forefront of research are summarized.

Dropped head syndrome: a rare adverse drug reaction identified in the FDA adverse event reporting system and review of case reports in the literature

BACKGROUND

Dropped head syndrome (DHS) is a relatively rare disease, and its potential relationship with drug exposure has been postulated but is poorly understood.

RESEARCH DESIGN AND METHODS

This retrospective study evaluated the adverse event reports of DHS in the FDA adverse event reporting system （FAERS) between 1 January 2004, to 31 March 2021. Empirical Bayes Geometric Means (EBGM) and the lower 95% one-sided CI of EBGM were calculated to identify disproportionate reporting of DHS associated with drugs. In addition, published case reports were identified in the PubMed, Embase and Cochrane Library up to 5 August 2021.

RESULTS

There were 193 reports of DHS in the FAERS, in which nervous system agents were most frequently reported, followed by antineoplastic and immunomodulating agents. Pramipexole, ropinirole, levodopa, pregabalin, rotigotine, cisplatin, imatinib and botulinum toxin showed disproportionality signal based each on more than 5 cases. Ten published DHS case reports were identified in the literature.

CONCLUSION

Our study provides a more explicit profile on the occurrences and characteristics of DHS associated with drugs by analyzing the FAERS data and indicates that exposure of certain drug showed disproportionality signal with the increased DHS risk, which suggests the importance of further clinical and observational investigations.

Precision drugging of the MAPK pathway in head and neck cancer

The mitogen-activating protein kinase (MAPK) pathway is central for cell proliferation, differentiation, and senescence. In human, germline defects of the pathway contribute to developmental and congenital head and neck disorders. Nearly 1/5 of head and neck squamous cell carcinoma (HNSCC) harbors MAPK pathway mutations, which are largely activating mutations. Yet, previous approaches targeting the MAPK pathway in HNSCC were futile. Most recent clinical evidences reveal remarkable, or even exceptional pharmacologic vulnerabilities of MAPK1-mutated, HRAS-mutated, KRAS-germline altered, as well as BRAF-mutated HNSCC patients with various targeted therapies, uncovering diverse opportunities for precision drugging this pathway at multiple “genetically condemned” nodes. Further, recent patient tumor omics unveil novel effects of MAPK aberrations on direct induction of CD8⁺ T cell recruitment into the HNSCC microenvironment, providing evidences for future investigation of precision immunotherapy for this large subset of patients. MAPK pathway-mutated HNSCC should warrant precision therapy assessments in vigorous manners.

Inhibition of MEK-ERK signaling reduces seizures in two mouse models of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a monogenic disorder characterized by hyperactivation of the mTOR signaling pathway and developmental brain malformations leading to intractable epilepsy. Although treatment with the recently approved mTOR inhibitor, everolimus, results in clinically relevant seizure suppression in up to 40% of TSC patients, seizures remain uncontrolled in a large number of cases, underscoring the need to identify novel treatment targets. The MEK-ERK signaling pathway has been found to be aberrantly activated in TSC and inhibition of MEK-ERK activity independently of mTOR rescued neuronal dendrite overgrowth in mice modeling TSC neuropathology. Here, we evaluated the efficacy of MEK-ERK inhibition on seizures in two mouse models of TSC. We found that treatment with the MEK inhibitor PD0325901 (mirdametinib) significantly reduced seizure activity in both TSC mouse models. These findings support inhibiting MEK-ERK activity as a potential alternative strategy to treat seizures in TSC.

WMMDCA: Prediction of Drug Responses by Weight-Based Modular Mapping in Cancer Cell Lines

Due to the high consumption of cost and time for experimental verification in clinical trials, drug response prediction by computational models have become important challenges. The existing drug response data in diverse cell lines enable prediction of potential sensitive associations. Here, we propose a weight-based modular mapping method, named as WMMDCA, to predict drug-cell line associations. The method fully considers the effects of drugs' chemical structural feature, and adds modular information into the network projection. Leave-one-out cross-validation was used to evaluate the predictive ability of WMMDCA, which showed the best performance among several state-of-the-art methods in not only the whole dataset but also the major tissue types of cell lines. Literature support of highly ranked potential associations was found manually, demonstrating the effectiveness of WMMDCA on drug response prediction.

Current Advances and Trends in KRAS Targeted Therapies for Colorectal Cancer

Kirsten Rat Sarcoma (KRAS) gene somatic point mutations is one of the most prominently mutated proto-oncogenes known to date, and accounts for approximately 60% of all colorectal cancer cases. One of the most exciting drug development areas against colorectal cancer is the targeting of undruggable kinases and kinase-substrate molecules, although whether and how they can be integrated with other therapies remains a question. Current clinical trial data have provided supporting evidence on the use of combination treatment involving MEK inhibitors and either one of the PI3K inhibitors for patients with metastatic colorectal cancer to avoid the development of resistance and provide effective therapeutic outcome rather than using a single agent alone. Many clinical trials are also ongoing to evaluate different combinations of these pathway inhibitors in combination with immunotherapy for patients with colorectal cancer whose current palliative treatment options are limited. Nevertheless, continued assessment of these targeted cancer therapies will eventually allow patients with colorectal cancer to be treated using a personalized medicine approach. In this review, the most recent scientific approaches and clinical trials targeting KRAS mutations directly or indirectly for the management of colorectal cancer are discussed.

Novel molecular targeted therapies for patients with neurofibromatosis type 1 with inoperable plexiform neurofibromas: a comprehensive review

Neurofibromatosis type 1 (NF1) is a genetic disorder that carries a higher risk of tumor development. Plexiform neurofibromas (PNs) are present in 50% of NF1 and cause significant morbidity when surgery is not feasible. Systemic therapies had not succeeded to reduce PN tumor volume until 2016 when the first trial with an MAPK/extracellular-signal-regulated kinase (MEK) inhibitor was published. We performed a systematic research on novel targeted therapies for patients with NF1 and PNs in PubMed, EMBASE, and conference abstracts with the last update in February 2021. Since 2016, seven trials have reported positive results with MEK inhibitors and other molecular targeted therapies (cabozantinib). Selumetinib has shown an overall response rate of 68% in children with NF1 and symptomatic inoperable PNs, and was associated with pain improvement and a manageable adverse events profile. This led to Food and Drug Administration (FDA) approval of selumetinib in May 2020. Recently, cabozantinib and mirdametinib have also proven their efficacy in adult population. Other MEK inhibitors such as trametinib and binimetinib have also communicated promising preliminary results. Ongoing trials in different populations and with intermittent dosing strategies are underway.

RASAL2 Confers Collateral MEK/EGFR Dependency in Chemoresistant Triple-Negative Breast Cancer

PURPOSE

While chemotherapy remains the standard treatment for triple-negative breast cancer (TNBC), identifying and managing chemoresistant tumors has proven elusive. We sought to discover hallmarks and therapeutically actionable features of refractory TNBC through molecular analysis of primary chemoresistant TNBC specimens.

EXPERIMENTAL DESIGN

We performed transcriptional profiling of tumors from a phase II clinical trial of platinum chemotherapy for advanced TNBC (TBCRC-009), revealing a gene expression signature that identified de novo chemorefractory tumors. We then employed pharmacogenomic data mining, proteomic and other molecular studies to define the therapeutic vulnerabilities of these tumors.

RESULTS

We reveal the RAS-GTPase-activating protein (RAS-GAP) RASAL2 as an upregulated factor that mediates chemotherapy resistance but also an exquisite collateral sensitivity to combination MAP kinase kinase (MEK1/2) and EGFR inhibitors in TNBC. Mechanistically, RASAL2 GAP activity is required to confer kinase inhibitor sensitivity, as RASAL2-high TNBCs sustain basal RAS activity through suppression of negative feedback regulators SPRY1/2, together with EGFR upregulation. Consequently, RASAL2 expression results in failed feedback compensation upon co-inhibition of MEK1/2 and EGFR that induces synergistic apoptosis in vitro and in vivo. In patients with TNBC, high RASAL2 levels predict clinical chemotherapy response and long-term outcomes, and are associated via direct transcriptional regulation with activated oncogenic Yes-Associated Protein (YAP). Accordingly, chemorefractory patient-derived TNBC models exhibit YAP activation, high RASAL2 expression, and tumor regression in response to MEK/EGFR inhibitor combinations despite well-tolerated intermittent dosing.

CONCLUSIONS

These findings identify RASAL2 as a mediator of TNBC chemoresistance that rewires MAPK feedback and cross-talk to confer profound collateral sensitivity to combination MEK1/2 and EGFR inhibitors.

Retinal toxicities of systemic anticancer drugs

Newer anticancer drugs have revolutionized cancer treatment in the last decade, but conventional chemotherapy still occupies a central position in many cancers, with combination therapy and newer methods of delivery increasing their efficacy while minimizing toxicities. We discuss the retinal toxicities of anticancer drugs with an emphasis on the mechanism of toxicity. Uveitis is seen with the use of v-raf murine sarcoma viral oncogene homolog B editing anticancer inhibitors as well as immunotherapy. Most of the cases are mild with only anterior uveitis, but severe cases of posterior uveitis, panuveitis, and Vogt-Koyanagi-Harada-like disease may also occur. In the retina, a transient neurosensory detachment is observed in almost all patients on mitogen-activated protein kinase kinase (MEK) inhibitors. Microvasculopathy is often seen with interferon α, but vascular occlusion is a more serious toxicity caused by interferon α and MEK inhibitors. Crystalline retinopathy with or without macular edema may occur with tamoxifen; however, even asymptomatic patients may develop cavitatory spaces seen on optical coherence tomography. A unique macular edema with angiographic silence is characteristic of taxanes. Delayed dark adaptation has been observed with fenretinide. Interestingly, this drug is finding potential application in Stargardt disease and age-related macular degeneration.

NF106: A Neurofibromatosis Clinical Trials Consortium Phase II Trial of the MEK Inhibitor Mirdametinib (PD-0325901) in Adolescents and Adults With NF1-Related Plexiform Neurofibromas

Patients with neurofibromatosis type 1 (NF1) frequently develop plexiform neurofibromas (PNs), which can cause significant morbidity. We performed a phase II trial of the MAPK/ERK kinase inhibitor, mirdametinib (PD-0325901), in patients with NF1 and inoperable PNs. The primary objective was response rate based on volumetric magnetic resonance imaging analysis.

Novel insights into the pathogenesis and treatment of NRAS mutant melanoma

INTRODUCTION

NRAS was the first mutated oncogene identified in melanoma and is currently the second most common driver mutation in this malignancy. For patients with NRAS^mutant advanced stage melanoma refractory to immunotherapy or with contraindications to immune-based regimens, there are few therapeutic options including low-efficacy chemotherapy regimens and binimetinib monotherapy. Here, we review recent advances in preclinical studies of molecular targets for NRAS mutant melanoma as well as the failures and successes of early-phase clinical trials. While there are no targeted therapies for NRAS-driven melanoma, there is great promise in approaches combining MEK inhibition with inhibitors of the focal adhesion kinase (FAK), inhibitors of autophagy pathways, and pan-RAF inhibitors.

AREAS COVERED

This review surveys new developments in all aspects of disease pathogenesis and potential treatment - including those that have failed, stalled, or progressed through various phases of preclinical and clinical development.

EXPERT OPINION

There are no currently approved targeted therapies for BRAF wild-type melanoma patients harboring NRAS driver mutations though an array of agents are in early phase clinical trials. The diverse strategies taken exploit combined MAP kinase signaling blockade with inhibition of cell cycle mediators, inhibition of the autophagy pathway, and alteration of kinases involved in actin cytoskeleton signaling. Future advances of developmental therapeutics into late stage trials may yield new options beyond immunotherapy for patients with advanced stage disease and NRAS mutation status.

Non-Steroidal Anti-Inflammatory Drugs Increase Cisplatin, Paclitaxel, and Doxorubicin Efficacy against Human Cervix Cancer Cells

This study shows that the non-steroidal anti-inflammatory drug (NSAID) celecoxib and its non-cyclooxygenase-2 (COX2) analogue dimethylcelecoxib (DMC) exert a potent inhibitory effect on the growth of human cervix HeLa multi-cellular tumor spheroids (MCTS) when added either at the beginning (“preventive protocol”; IC₅₀ = 1 ± 0.3 nM for celecoxib and 10 ± 2 nM for DMC) or after spheroid formation (“curative protocol”; IC₅₀ = 7.5 ± 2 µM for celecoxib and 32 ± 10 µM for DMC). These NSAID IC₅₀ values were significantly lower than those attained in bidimensional HeLa cells (IC₅₀ = 55 ± 9 µM celecoxib and 48 ± 2 µM DMC) and bidimensional non-cancer cell cultures (3T3 fibroblasts and MCF-10A mammary gland cells with IC₅₀ from 69 to >100 µM, after 24 h). The copper-based drug casiopeina II-gly showed similar potency against HeLa MCTS. Synergism analysis showed that celecoxib, DMC, and casiopeinaII-gly at sub-IC₅₀ doses increased the potency of cisplatin, paclitaxel, and doxorubicin to hinder HeLa cell proliferation through a significant abolishment of oxidative phosphorylation in bidimensional cultures, with no apparent effect on non-cancer cells (therapeutic index >3.6). Similar results were attained with bidimensional human cervix cancer SiHa and human glioblastoma U373 cell cultures. In HeLa MCTS, celecoxib, DMC and casiopeina II-gly increased cisplatin toxicity by 41–85%. These observations indicated that celecoxib and DMC used as adjuvant therapy in combination with canonical anti-cancer drugs may provide more effective alternatives for cancer treatment.

Hypermethylation of the IRAK3-Activated MAPK Signaling Pathway to Promote the Development of Glioma

Objective

This study aimed to elucidate the molecular mechanism underlying the involvement of abnormal DNA methylation in the development of glioma and identify potential new targets for glioma therapy.

Methods

The GSE79122 chip achieved from the Gene Expression Omnibus (GEO) database containing 69 glioma samples and 9 normal samples was analyzed. Methylation-specific polymerase chain reaction (MS-PCR or MSP), reverse transcription-PCR, and Western blot analysis were used to confirm the methylation level and expression level of the interleukin receptor-associated kinase (IRAK3) gene in glioma cells, 36 glioma samples, and the corresponding normal samples. In vitro, the proliferation, apoptosis rate, migration, and invasion abilities of glioma cells were detected by Cell Counting Kit-8 assay, Transwell assay, enzyme-linked immunosorbent assay, and flow cytometry, respectively. Besides, the xenograft assay of nude mice was used to confirm the effect of the IRAK3 on glioma in vivo.

Results

Microarray analysis showed that the IRAK3 was one of the most hypermethylated genes in glioma, and the related mitogen-activated protein kinase (MAPK) signaling pathway was activated. More experiments supported the higher methylation level and lower expression level of the IRAK3 in glioma tissues and cell lines. The viability, migration, and invasion ability of glioma cells significantly reduced and the apoptosis rate increased with the overexpression and demethylation of the IRAK3 in vitro. Besides, treatment with the MAPK signaling pathway inhibitor PD325901 alone or the overexpression or demethylation of the IRAK3 had a similar effect as the overexpression or demethylation of the IRAK3 alone in glioma cells. In vivo, xenotransplantation experiments in nude mice confirmed that the overexpression and demethylation of the IRAK3 and suppression of the MAPK signaling pathway inhibited the development of glioma.

Conclusion

IRAK3 inhibited the development of glioma progression through the MAPK signaling pathway.

Safety of BRAF+MEK Inhibitor Combinations: Severe Adverse Event Evaluation

Aim: The selective BRAF and MEK inhibitors (BRAFi+MEKi) have substantially improved the survival of melanoma patients with BRAF V600 mutations. However, BRAFi+MEKi can also cause severe or fatal outcomes. We aimed to identify and compare serious adverse events (sAEs) that are significantly associated with BRAFi+MEKi. Methods: In this pharmacovigilance study, we reviewed FDA Adverse Event Reporting System (FAERS) data in order to detect sAE reporting in patients treated with the combination therapies vemurafenib+cobimetinib (V+C), dabrafenib+trametinib (D+T) and encorafenib+binimetinib (E+B). We evaluated the disproportionate reporting of BRAFi+MEKi-associated sAEs. Significant associations were further analyzed to identify combination-specific safety signals among BRAFi+MEKi. Results: From January 2018 through June 2019, we identified 11,721 sAE reports in patients receiving BRAFi+MEKi. Comparison of BRAFi+MEKi combinations demonstrates that skin toxicities, including Stevens–Johnson syndrome, were disproportionally reported using V+C, with an age-adjusted reporting odds ratio (adj. ROR) of 3.4 (95%CI, 2.9–4.0), whereas fever was most significantly associated with D+T treatment with an adj. ROR of 1.9 (95%CI, 1.5–2.4). Significant associations using E+B treatment include peripheral neuropathies (adj. ROR 2.7; 95%CI, 1.2–6.1) and renal disorders (adj. ROR 4.1; 95%CI, 1.3–12.5). Notably, we found an increase in the proportion of Guillain–Barré syndrome reports (adj. ROR 8.5; 95%CI, 2.1–35.0) in patients administered E+B. Conclusion: BRAFi+MEKi combinations share a similar safety profile attributed to class effects, yet concomitantly, these combinations display distinctive effects that can dramatically impact patients’ health. Owing to the limitations of pharmacovigilance studies, some findings warrant further validation. However, the possibility of an increased risk for these events should be considered in patient care.

Qualitative Ras pathway signature for cetuximab therapy reveals resistant mechanism in colorectal cancer

Cetuximab therapy, which heavily relies on the activation of Ras pathway, has been used in KRAS, NRAS, BRAF, and PIK3CA wild-type colorectal cancer (CRC) (Ras-normal). However, the response rate only reached 60%, due to false-negative mutation detection and mutation-like transcriptome features in wild-type patients. Herein, by integrating RNA-seq, microarray, and mutation data, we developed a Ras pathway signature by characterizing KRAS/NRAS/BRAF/PIK3CA mutations to identify the hidden nonresponders from the Ras-normal patients by mutation detection. Using public and in-house data of CRC patients treated with cetuximab, discovery of the signature could identify cetuximab-resistant samples from the Ras-normal samples. Cetuximab resistance-related genes, such as PTEN, were significantly and frequently mutated in the identified Ras-activated samples, whereas two cetuximab sensitivity-related genes, APC and TP53, showed comutation and significantly higher mutation frequencies in the remaining Ras-normal samples. Furthermore, all the NF1- and BCL2L1-mutated samples were identified as Ras-activated from the Ras-normal samples by the Ras pathway signature with significantly under-regulated expression. Genes co-expressed with the two genes were both involved in Ras signaling pathway, the out-of-control of which could be attributed by the genes' loss-of-function mutations. To improve the treatment of cetuximab in CRC, NF1 and BCL2L1 could be used as complementary detection technique to those applied in clinical. In conclusion, the proposed Ras pathway signature could identify the hidden CRC patients resistant to cetuximab therapy and help to reveal resistance mechanisms.

Current Advances in the Treatment of BRAF-Mutant Melanoma

Melanoma is the most lethal form of skin cancer. Melanoma is usually curable with surgery if detected early, however, treatment options for patients with metastatic melanoma are limited and the five-year survival rate for metastatic melanoma had been 15-20% before the advent of immunotherapy. Treatment with immune checkpoint inhibitors has increased long-term survival outcomes in patients with advanced melanoma to as high as 50% although individual response can vary greatly. A mutation within the MAPK pathway leads to uncontrollable growth and ultimately develops into cancer. The most common driver mutation that leads to this characteristic overactivation in the MAPK pathway is the B-RAF mutation. Current combinations of BRAF and MEK inhibitors that have demonstrated improved patient outcomes include dabrafenib with trametinib, vemurafenib with cobimetinib or encorafenib with binimetinib. Treatment with BRAF and MEK inhibitors has met challenges as patient responses began to drop due to the development of resistance to these inhibitors which paved the way for development of immunotherapies and other small molecule inhibitor approaches to address this. Resistance to these inhibitors continues to push the need to expand our understanding of novel mechanisms of resistance associated with treatment therapies. This review focuses on the current landscape of how resistance occurs with the chronic use of BRAF and MEK inhibitors in BRAF-mutant melanoma and progress made in the fields of immunotherapies and other small molecules when used alone or in combination with BRAF and MEK inhibitors to delay or circumvent the onset of resistance for patients with stage III/IV BRAF mutant melanoma.

Identifying "Many-to-Many" Relationships between Gene-Expression Data and Drug-Response Data via Sparse Binary Matching

Identifying gene-drug patterns is a critical step in pharmacology for unveiling disease mechanisms and drug discovery. The availability of high-throughput technologies accumulates massive large-scale pharmacological and genomic data, and thus provides a new substantial opportunity to deeply understand how the oncogenic genes and the therapeutic drugs relate to each other. However, most previous studies merely used the pharmacological and genomic datasets without any prior knowledge to infer the gene-drug patterns. Here, we proposed a novel network-guided sparse binary matching model (NSBM) to decode these relationships hidden in the datasets. Not only the large-scale gene-expression data and drug-response data are jointly analyzed in our method, but also the additional prior information of genes and drugs are integrated into the form of network-based regularization. The essential structure of the NSBM model is a convex quadratic minimization problem with network-based penalties. It was demonstrated to be superior when compared with two benchmark methods through extensive experiments on both synthetic and empirical data. Posterior validation, including gene-ontology and enrichment analysis, confirmed the effectiveness of NSBM in revealing gene-drug patterns on a large-scale heterogeneous data source.

Somatic loss of PIK3R1 may sensitize breast cancer to inhibitors of the MAPK pathway

PURPOSE

The PI3K pathway, which includes the PI3K catalytic subunits p110α (PIK3CA) and the PI3K regulatory subunit p85α (PIK3R1), is the most frequently altered pathway in cancer. We encountered a breast cancer patient whose tumor contained a somatic alteration in PIK3R1. Some commercial sequencing platforms suggest that somatic mutations in PIK3R1 may sensitize cancers to drugs that inhibit the mammalian target of rapamycin (mTOR). However, a review of the preclinical and clinical literature did not find evidence substantiating that hypothesis. The purpose of this study was to knock out PIK3R1 in order to determine the optimal therapeutic approach for breast cancers lacking p85α.

METHODS

We created an isogenic cellular system by knocking out both alleles of the PIK3R1 gene in the non-tumorigenic human breast cell line MCF-10A. Knockout cells were compared with wild-type cells by measuring growth, cellular signaling, and response to drugs.

RESULTS

We observed hyperphosphorylation of MEK in these knockouts, which sensitized PIK3R1-null cells to a MEK inhibitor, trametinib. However, they were not sensitized to the mTOR inhibitor, everolimus.

CONCLUSIONS

Our findings suggest that breast cancers with loss of p85α may not respond to mTOR inhibition, but may be sensitive to MEK inhibition.

Targeting the ERK Signaling Pathway in Melanoma

The discovery of the role of the RAS/RAF/MEK/ERK pathway in melanomagenesis and its progression have opened a new era in the treatment of this tumor. Vemurafenib was the first specific kinase inhibitor approved for therapy of advanced melanomas harboring BRAF-activating mutations, followed by dabrafenib and encorafenib. However, despite the excellent results of first-generation kinase inhibitors in terms of response rate, the average duration of the response was short, due to the onset of genetic and epigenetic resistance mechanisms. The combination therapy with MEK inhibitors is an excellent strategy to circumvent drug resistance, with the additional advantage of reducing side effects due to the paradoxical reactivation of the MAPK pathway. The recent development of RAS and extracellular signal-related kinases (ERK) inhibitors promises to add new players for the ultimate suppression of this signaling pathway and the control of pathway-related drug resistance. In this review, we analyze the pharmacological, preclinical, and clinical trial data of the various MAPK pathway inhibitors, with a keen interest for their clinical applicability in the management of advanced melanoma.

Acute motor and sensory axonal neuropathy related to treatment with MEK inhibitors in a patient with advanced melanoma

Approximately one-half of advanced cutaneous melanomas have a V600 mutation in the BRAF gene that activates the mitogen-activated protein kinase pathway. The combination of BRAF plus MEK inhibitors is one of the most effective treatments for these patients. Severe neurological toxicities have been reported in the literature. However, these toxicities are very rare. Here, we present one patient with acute motor and sensory axonal neuropathy, which is a subtype of Guillain-Barre syndrome, secondary to treatment with MEK inhibitors. This side effect had never been described as related to these agents. However, the mitogen-activated protein kinase pathway can be involved in Guillain-Barre syndrome, and awareness of early neurological injury signs is important in patients treated with MEK inhibitors.

Machine Learning Detects Pan-cancer Ras Pathway Activation in The Cancer Genome Atlas

Precision oncology uses genomic evidence to match patients with treatment but often fails to identify all patients who may respond. The transcriptome of these "hidden responders" may reveal responsive molecular states. We describe and evaluate a machine-learning approach to classify aberrant pathway activity in tumors, which may aid in hidden responder identification. The algorithm integrates RNA-seq, copy number, and mutations from 33 different cancer types across The Cancer Genome Atlas (TCGA) PanCanAtlas project to predict aberrant molecular states in tumors. Applied to the Ras pathway, the method detects Ras activation across cancer types and identifies phenocopying variants. The model, trained on human tumors, can predict response to MEK inhibitors in wild-type Ras cell lines. We also present data that suggest that multiple hits in the Ras pathway confer increased Ras activity. The transcriptome is underused in precision oncology and, combined with machine learning, can aid in the identification of hidden responders.

Current Development Status of MEK Inhibitors

The current development status of mitogen-activated protein kinase kinase (MEK) inhibitors, including the preclinical data and clinical study progress, has been summarized in this review. Different MEK inhibitors, possessing specific physicochemical properties and bioactivity characteristics, may provide different options for patients seeking treatment for cancer. Moreover, the combination of the MEK inhibitors with other therapies-such as chemotherapy, targeted therapy, and immunotherapy-may be a promising approach for clinical use.

Heterogeneity Aware Random Forest for Drug Sensitivity Prediction

Samples collected in pharmacogenomics databases typically belong to various cancer types. For designing a drug sensitivity predictive model from such a database, a natural question arises whether a model trained on diverse inter-tumor heterogeneous samples will perform similar to a predictive model that takes into consideration the heterogeneity of the samples in model training and prediction. We explore this hypothesis and observe that ensemble model predictions obtained when cancer type is known out-perform predictions when that information is withheld even when the samples sizes for the former is considerably lower than the combined sample size. To incorporate the heterogeneity idea in the commonly used ensemble based predictive model of Random Forests, we propose Heterogeneity Aware Random Forests (HARF) that assigns weights to the trees based on the category of the sample. We treat heterogeneity as a latent class allocation problem and present a covariate free class allocation approach based on the distribution of leaf nodes of the model ensemble. Applications on CCLE and GDSC databases show that HARF outperforms traditional Random Forest when the average drug responses of cancer types are different.

TAMH: A Useful In Vitro Model for Assessing Hepatotoxic Mechanisms

In vitro models for hepatotoxicity can be useful tools to predict in vivo responses. In this review, we discuss the use of the transforming growth factor-α transgenic mouse hepatocyte (TAMH) cell line, which is an attractive model to study drug-induced liver injury due to its ability to retain a stable phenotype and express drug-metabolizing enzymes. Hepatotoxicity involves damage to the liver and is often associated with chemical exposure. Since the liver is a major site for drug metabolism, drug-induced liver injury is a serious health concern for certain agents. At the molecular level, various mechanisms may protect or harm the liver during drug-induced hepatocellular injury including signaling pathways and endogenous factors (e.g., Bcl-2, GSH, Nrf2, or MAPK). The interplay between these and other pathways in the hepatocyte can change upon drug or drug metabolite exposure leading to intracellular stress and eventually cell death and liver injury. This review focuses on mechanistic studies investigating drug-induced toxicity in the TAMH line and how alterations to hepatotoxic mechanisms in this model relate to the in vivo situation. The agents discussed herein include acetaminophen (APAP), tetrafluoroethylcysteine (TFEC), flutamide, PD0325901, lapatinib, and flupirtine.

Therapeutic potential of targeting acinar cell reprogramming in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a common pancreatic cancer and the fourth leading cause of cancer death in the United States. Treating this life-threatening disease remains challenging due to the lack of effective prognosis, diagnosis and therapy. Apart from pancreatic duct cells, acinar cells may also be the origin of PDAC. During pancreatitis or combined with activating KRas(G12D) mutation, acinar cells lose their cellular identity and undergo a transdifferentiation process called acinar-to-ductal-metaplasia (ADM), forming duct cells which may then transform into pancreatic intraepithelial neoplasia (PanIN) and eventually PDAC. During ADM, the activation of mitogen-activated protein kinases, Wnt, Notch and phosphatidylinositide 3-kinases/Akt signaling inhibits the transcription of acinar-specific genes, including Mist and amylase, but promotes the expression of ductal genes, such as cytokeratin-19. Inhibition of this transdifferentiation process hinders the development of PanIN and PDAC. In addition, the transdifferentiated cells regain acinar identity, indicating ADM may be a reversible process. This provides a new therapeutic direction in treating PDAC through cancer reprogramming. Many studies have already demonstrated the success of switching PanIN/PDAC back to normal cells through the use of PD325901, the expression of E47, and the knockdown of Dickkopf-3. In this review, we discuss the signaling pathways involved in ADM and the therapeutic potential of targeting reprogramming in order to treat PDAC.

Combinatorial treatment using targeted MEK and SRC inhibitors synergistically abrogates tumor cell growth and induces mesenchymal-epithelial transition in non-small-cell lung carcinoma

Oncogenesis in non-small cell lung cancer (NSCLC) is regulated by a complex signal transduction network. Single-agent targeted therapy fails frequently due to treatment insensitivity and acquired resistance. In this study, we demonstrate that co-inhibition of the MAPK and SRC pathways using a PD0325901 and Saracatinib kinase inhibitor combination can abrogate tumor growth in NSCLC. PD0325901/Saracatinib at 0.25:1 combination was screened against a panel of 28 NSCLC cell lines and 68% of cell lines were found to be sensitive (IC₅₀ < 2 μM) to this combination. In Snail1 positive NSCLC lines, the drug combination complementarily enhanced mesenchymal-epithelial transition (MET), increasing both E-cadherin and Plakoglobin expression, and reducing Snail1, FAK and PXN expression. In addition, the drug combination abrogated cell migration and matrigel invasion. The co-inhibition of MAPK and SRC induced strong G1/G0 cell cycle arrest in the NSCLC lines, inhibited anchorage independent growth and delayed tumor growth in H460 and H358 mouse xenografts. These data provide rationale for further investigating the combination of MAPK and SRC pathway inhibitors in advanced stage NSCLC.

Allosteric modulators of MEK1: drug design and discovery

Mitogen-activated protein kinase kinase (MAPKK, MEK) mediates signal transduction, controlling cell proliferation and survival. MEK occupies a key downstream position in the Ras-Raf-MEK-ERK signaling pathway, implying that inhibition of MEK will potently suppress tumor cell growth, with potential applications in cancer therapy. Based on the promising therapeutic effects of MEK modulators, continued efforts have been made in this class. Here, we review the discovery and development of MEK1 allosteric modulators, classifying them into four structural groups. The allosteric mechanisms and recent clinical progress involving these modulators are also reviewed.

Preclinical assessments of the MEK inhibitor PD-0325901 in a mouse model of Neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a genetic disorder that predisposes affected individuals to formation of benign neurofibromas, peripheral nerve tumors that can be associated with significant morbidity. Loss of the NF1 Ras-GAP protein causes increased Ras-GTP, and we previously found that inhibiting MEK signaling downstream of Ras can shrink established neurofibromas in a genetically engineered murine model.

PROCEDURES

We studied effects of MEK inhibition using 1.5 mg/kg/day PD-0325901 prior to neurofibroma onset in the Nf1 (flox/flox); Dhh-Cre mouse model. We also treated mice with established tumors at 0.5 and 1.5 mg/kg/day doses of PD-0325901. We monitored tumor volumes using MRI and volumetric measurements, and measured pharmacokinetic and pharmacodynamic endpoints.

RESULTS

Early administration significantly delayed neurofibroma development as compared to vehicle controls. When treatment was discontinued neurofibromas grew, but no rebound effect was observed and neurofibromas remained significantly smaller than controls. Low dose treatment of mice with PD-0325901 resulted in neurofibroma shrinkage equivalent to that observed at higher doses. Tumor cell proliferation decreased, although less than at higher doses with drug. Tumor blood vessels per area correlated with tumor shrinkage.

CONCLUSIONS

Neurofibroma development was not prevented by MEK inhibition, beginning at 1 month of age, but tumor size was controlled by early treatment. Moreover, treatment with PD-0325901 at very low doses may shrink neurofibromas while minimizing toxicity. These studies highlight how genetically engineered mouse models can guide clinical trial design.

Major therapeutic developments and current challenges in advanced melanoma

Malignant melanoma is rising in incidence. The treatment options have been very limited but advances in molecular biology and immunology have led to a greater understanding of the pathogenesis of the disease. Four drugs have been approved for the treatment of advanced melanoma in the past 2 years and two new classes of agents have recently been shown to lead to durable responses in a substantial minority of patients. The identification of biomarkers has helped clinicians and researchers segregate patients into molecular subgroups, which facilitates the selection of therapy. Preliminary work has begun on determining the ideal sequences of the various therapies. Investigations have been carried out on why these treatments work and what the mechanisms of resistance are to these therapies. It is hoped that combinations of therapies will emerge that lead to a high percentage of durable responses.

MEK1 is associated with carboplatin resistance and is a prognostic biomarker in epithelial ovarian cancer

BACKGROUND

Primary systemic treatment for ovarian cancer is surgery, followed by platinum based chemotherapy. Platinum resistant cancers progress/recur in approximately 25% of cases within six months. We aimed to identify clinically useful biomarkers of platinum resistance.

METHODS

A database of ovarian cancer transcriptomic datasets including treatment and response information was set up by mining the GEO and TCGA repositories. Receiver operator characteristics (ROC) analysis was performed in R for each gene and these were then ranked using their achieved area under the curve (AUC) values. The most significant candidates were selected and in vitro functionally evaluated in four epithelial ovarian cancer cell lines (SKOV-3-, CAOV-3, ES-2 and OVCAR-3), using gene silencing combined with drug treatment in viability and apoptosis assays. We collected 94 tumor samples and the strongest candidate was validated by IHC and qRT-PCR in these.

RESULTS

All together 1,452 eligible patients were identified. Based on the ROC analysis the eight most significant genes were JRK, CNOT8, RTF1, CCT3, NFAT2CIP, MEK1, FUBP1 and CSDE1. Silencing of MEK1, CSDE1, CNOT8 and RTF1, and pharmacological inhibition of MEK1 caused significant sensitization in the cell lines. Of the eight genes, JRK (p = 3.2E-05), MEK1 (p = 0.0078), FUBP1 (p = 0.014) and CNOT8 (p = 0.00022) also correlated to progression free survival. The correlation between the best biomarker candidate MEK1 and survival was validated in two independent cohorts by qRT-PCR (n = 34, HR = 5.8, p = 0.003) and IHC (n = 59, HR = 4.3, p = 0.033).

CONCLUSION

We identified MEK1 as a promising prognostic biomarker candidate correlated to response to platinum based chemotherapy in ovarian cancer.

Targeting MAPK pathway in melanoma therapy

New drugs targeting the mitogen-activated protein kinase (MAPK) pathway have generated striking clinical response in melanoma therapy. From the discovery of BRAF mutation in melanoma in 2002, to the approval of first BRAF inhibitor vemurafenib for melanoma treatment by the US Food and Drug Administration in 2011, therapies targeting the MAPK pathway have been proven effective in less than a decade. The success of vemurafenib stimulated more intensive investigation of the molecular mechanisms of melanoma pathogenesis and development of new treatment strategies targeting specific molecules in MAPK pathway. Although selective BRAF inhibitors and MEK inhibitors demonstrated improved overall survival of metastatic melanoma patients, limited duration or development of resistance to BRAF inhibitors have been reported. Patients with metastatic melanoma still face very poor prognosis and lack of clarified therapies. Studies and multiple clinical trials on more potent and selective small molecule inhibitory compounds to further improve the clinical effects and overcome drug resistance are underway. In this review, we analyzed the therapeutic potentials of each member of the MAPK signaling pathway, summarized important MAPK-inhibiting drugs, and discussed the promising combination treatment targeting multiple targets in melanoma therapy, which may overcome the drawbacks of current drugs treatment.

Dual pharmacological targeting of the MAP kinase and PI3K/mTOR pathway in preclinical models of colorectal cancer

BACKGROUND

The activation of the MAPK and PI3K/AKT/mTOR pathways is implicated in the majority of cancers. Activating mutations in both of these pathways has been described in colorectal cancer (CRC), thus indicating their potential as therapeutic targets. This study evaluated the combination of a PI3K/mTOR inhibitor (PF-04691502/PF-502) in combination with a MEK inhibitor (PD-0325901/PD-901) in CRC cell lines and patient-derived CRC tumor xenograft models (PDTX).

MATERIALS AND METHODS

The anti-proliferative effects of PF-502 and PD-901 were assessed as single agents and in combination against a panel of CRC cell lines with various molecular backgrounds. Synergy was evaluated using the Bliss Additivity method. In selected cell lines, we investigated the combination effects on downstream effectors by immunoblotting. The combination was then evaluated in several fully genetically annotated CRC PDTX models.

RESULTS

The in vitro experiments demonstrated a wide range of IC50 values for both agents against a cell line panel. The combination of PF-502 and PD-901 demonstrated synergistic anti-proliferative activity with Bliss values in the additive range. As expected, p-AKT and p-ERK were downregulated by PF-502 and PD-901, respectively. In PDTX models, following a 30-day exposure to PF-502, PD-901 or the combination, the combination demonstrated enhanced reduction in tumor growth as compared to either single agent regardless of KRAS or PI3K mutational status.

CONCLUSIONS

The combination of a PI3K/mTOR and a MEK inhibitor demonstrated enhanced anti-proliferative effects against CRC cell lines and PDTX models.

Effects of MEK inhibitors GSK1120212 and PD0325901 in vivo using 10-plex quantitative proteomics and phosphoproteomics

Multiplexed isobaric tag based quantitative proteomics and phosphoproteomics strategies can comprehensively analyze drug treatments effects on biological systems. Given the role of mitogen-activated protein/extracellular signal-regulated kinase (MEK) signaling in cancer and mitogen-activated protein kinase (MAPK)-dependent diseases, we sought to determine if this pathway could be inhibited safely by examining the downstream molecular consequences. We used a series of tandem mass tag 10-plex experiments to analyze the effect of two MEK inhibitors (GSK1120212 and PD0325901) on three tissues (kidney, liver, and pancreas) from nine mice. We quantified ∼ 6000 proteins in each tissue, but significant protein-level alterations were minimal with inhibitor treatment. Of particular interest was kidney tissue, as edema is an adverse effect of these inhibitors. From kidney tissue, we enriched phosphopeptides using titanium dioxide (TiO2 ) and quantified 10 562 phosphorylation events. Further analysis by phosphotyrosine peptide immunoprecipitation quantified an additional 592 phosphorylation events. Phosphorylation motif analysis revealed that the inhibitors decreased phosphorylation levels of proline-x-serine-proline (PxSP) and serine-proline (SP) sites, consistent with extracellular-signal-regulated kinase (ERK) inhibition. The MEK inhibitors had the greatest decrease on the phosphorylation of two proteins, Barttin and Slc12a3, which have roles in ion transport and fluid balance. Further studies will provide insight into the effect of these MEK inhibitors with respect to edema and other adverse events in mouse models and human patients.

MEK inhibition in the treatment of advanced melanoma

The RAS-RAF-MEK-ERK pathway is considered to be the most important signal transduction pathway in melanoma, and alterations in this pathway via various genetic mutations, such as BRAF and NRAS mutations, are known to be important drivers of melanomagenesis. As MEK is an essential intermediary kinase protein within this pathway, inhibition of MEK has been of a great interest as a molecular target therapy in melanoma. In fact, trametinib, a selective MEK inhibitor, has been shown to have a survival benefit over cytotoxic chemotherapy in patients with V600 BRAF-mutant metastatic melanoma, leading to the FDA approval for this patient population. MEK inhibitors may also be useful in treatment of advanced melanoma harboring other genetic mutations, such as NRAS and GNAQ/GNA11 mutations. Here, we review and discuss the preclinical and clinical data regarding MEK inhibitors and their role in the treatment of advanced melanoma.

Modulation of endochondral ossification by MEK inhibitors PD0325901 and AZD6244 (Selumetinib)

MEK inhibitors (MEKi) PD0325901 and AZD6244 (Selumetinib) are drugs currently under clinical investigation for cancer treatment, however the Ras-MAPK pathway is also an important mediator of normal bone cell differentiation and function. In this study we examined the effects of these compounds on endochondral processes using both in vitro and in vivo models. Treatment with PD0325901 or AZD6244 significantly increased Runx2 and Alkaline phosphate gene expression in calvarial osteoblasts and decreased TRAP+ cells in induced osteoclast cultures. To test the effects of these drugs on bone healing, C57/Bl6 mice underwent a closed tibial fracture and were treated with PD0325901 or AZD6244 at 10mg/kg/day. Animals were culled at day 10 and at day 21 post-fracture for analysis of the fracture callus and the femoral growth plate in the contralateral leg. MEKi treatment markedly increased cartilage volume in the soft callus at day 10 post-fracture (+60% PD0325901, +20% AZD6244) and continued treatment led to a delay in cartilage remodeling. At the growth plate, we observed an increase in the height of the hypertrophic zone relative to the proliferative zone of +78% in PD0325901 treated mice. Osteoclast surface was significantly decreased both at the terminal end of the growth plate and within the fracture calluses of MEKi treated animals. The mechanistic effects of MEKi on genes encoding cartilage matrix proteins and catabolic enzymes were examined in articular chondrocyte cultures. PD0325901 or AZD6244 led to increased matrix protein expression (Col2a1 and Acan) and decreased expression of catabolic factors (Mmp13 and Adamts-5). Taken together, these data support the hypothesis that MEKi treatment can impact chondrocyte hypertrophy, matrix resorption, and fracture healing. These compounds can also affect bone architecture by expanding the hypertrophic zone of the growth plate and reducing osteoclast surface systemically.

Mek inhibition results in marked antitumor activity against metastatic melanoma patient-derived melanospheres and in melanosphere-generated xenografts

One of the key oncogenic pathways involved in melanoma aggressiveness, development and progression is the RAS/BRAF/MEK pathway, whose alterations are found in most patients. These molecular anomalies are promising targets for more effective anti-cancer therapies. Some Mek inhibitors showed promising antitumor activity, although schedules and doses associated with low systemic toxicity need to be defined. In addition, it is now accepted that cancers can arise from and be maintained by the cancer stem cells (CSC) or tumor-initiating cells (TIC), commonly expanded in vitro as tumorspheres from several solid tumors, including melanoma (melanospheres). Here, we investigated the potential targeting of MEK pathway by exploiting highly reliable in vitro and in vivo pre-clinical models of melanomas based on melanospheres, as melanoma initiating cells (MIC) surrogates. MEK inhibition, through PD0325901, provided a successful strategy to affect survival of mutated-BRAF melanospheres and growth of wild type-BRAF melanospheres. A marked citotoxicity was observed in differentated melanoma cells regardless BRAF mutational status. PD0325901 treatment, dramatically inhibited growth of melanosphere-generated xenografts and determined impaired tumor vascularization of both mutated- and wild type-BRAF tumors, in the absence of mice toxicity. These results suggest that MEK inhibition might represent a valid treatment option for patients with both mutated- or wild type-BRAF melanomas, affecting tumor growth through multiple targets.

Ras-Mek-Erk signaling regulates Nf1 heterozygous neointima formation

Neurofibromatosis type 1 (NF1) results from mutations in the NF1 tumor-suppressor gene, which encodes neurofibromin, a negative regulator of diverse Ras signaling cascades. Arterial stenosis is a nonneoplastic manifestation of NF1 that predisposes some patients to debilitating morbidity and sudden death. Recent murine studies demonstrate that Nf1 heterozygosity (Nf1(+/-)) in monocytes/macrophages significantly enhances intimal proliferation after arterial injury. However, the downstream Ras effector pathway responsible for this phenotype is unknown. Based on in vitro assays demonstrating enhanced extracellular signal-related kinase (Erk) signaling in Nf1(+/-) macrophages and vascular smooth muscle cells and in vivo evidence of Erk amplification without alteration of phosphatidylinositol 3-kinase signaling in Nf1(+/-) neointimas, we tested the hypothesis that Ras-Erk signaling regulates intimal proliferation in a murine model of NF1 arterial stenosis. By using a well-established in vivo model of inflammatory cell migration and standard cell culture, neurofibromin-deficient macrophages demonstrate enhanced sensitivity to growth factor stimulation in vivo and in vitro, which is significantly diminished in the presence of PD0325901, a specific inhibitor of Ras-Erk signaling in phase 2 clinical trials for cancer. After carotid artery injury, Nf1(+/-) mice demonstrated increased intimal proliferation compared with wild-type mice. Daily administration of PD0325901 significantly reduced Nf1(+/-) neointima formation to levels of wild-type mice. These studies identify the Ras-Erk pathway in neurofibromin-deficient macrophages as the aberrant pathway responsible for enhanced neointima formation.

The intersection of immune-directed and molecularly targeted therapy in advanced melanoma: where we have been, are, and will be

In three years, four drugs have gained regulatory approval for the treatment of metastatic and unresectable melanoma, with at least seven other drugs having recently completed, currently in, or soon to be in phase III clinical testing. This amazing achievement has been made following a remarkable increase of knowledge in molecular biology and immunology that led to the identification of high-valued therapeutic targets and the clinical development of agents that effectively engage and inhibit these targets. The discovery of either effective molecularly targeted therapies or immunotherapies would have led to dramatic improvements to the standard-of-care treatment of melanoma. However, through parallel efforts that have showcased the efficacy of small-molecule BRAF and MAP-ERK kinase (MEK) inhibitors, as well as the immune checkpoint inhibitors, namely ipilimumab and the anti-PD1/PDL1 antibodies (lambrolizumab, nivolumab, MPDL3280), an opportunity exists to transform the treatment of melanoma specifically and cancer generally by exploring rational combinations of molecularly targeted therapies, immunotherapies, and molecular targeted therapies with immunotherapies. This overview presents the historical context to this therapeutic revolution, reviews the benefits and limitations of current therapies, and provides a look ahead at where the field is headed.

MEK inhibition exhibits efficacy in human and mouse neurofibromatosis tumors

Neurofibromatosis type 1 (NF1) patients develop benign neurofibromas and malignant peripheral nerve sheath tumors (MPNST). These incurable peripheral nerve tumors result from loss of NF1 tumor suppressor gene function, causing hyperactive Ras signaling. Activated Ras controls numerous downstream effectors, but specific pathways mediating the effects of hyperactive Ras in NF1 tumors are unknown. We performed cross-species transcriptome analyses of mouse and human neurofibromas and MPNSTs and identified global negative feedback of genes that regulate Ras/Raf/MEK/ERK signaling in both species. Nonetheless, ERK activation was sustained in mouse and human neurofibromas and MPNST. We used a highly selective pharmacological inhibitor of MEK, PD0325901, to test whether sustained Ras/Raf/MEK/ERK signaling contributes to neurofibroma growth in a neurofibromatosis mouse model (Nf1(fl/fl);Dhh-Cre) or in NF1 patient MPNST cell xenografts. PD0325901 treatment reduced aberrantly proliferating cells in neurofibroma and MPNST, prolonged survival of mice implanted with human MPNST cells, and shrank neurofibromas in more than 80% of mice tested. Our data demonstrate that deregulated Ras/ERK signaling is critical for the growth of NF1 peripheral nerve tumors and provide a strong rationale for testing MEK inhibitors in NF1 clinical trials.