Molecular pathways: the basis for rational combination using MEK inhibitors in KRAS-mutant cancers

Trametinib sensitizes KRAS-mutant lung adenocarcinoma tumors to PD-1/PD-L1 axis blockade via Id1 downregulation

BACKGROUND

The identification of novel therapeutic strategies to overcome resistance to the MEK inhibitor trametinib in mutant KRAS lung adenocarcinoma (LUAD) is a challenge. This study analyzes the effects of trametinib on Id1 protein, a key factor involved in the KRAS oncogenic pathway, and investigates the role of Id1 in the acquired resistance to trametinib as well as the synergistic anticancer effect of trametinib combined with immunotherapy in KRAS-mutant LUAD.

METHODS

We evaluated the effects of trametinib on KRAS-mutant LUAD by Western blot, RNA-seq and different syngeneic mouse models. Genetic modulation of Id1 expression was performed in KRAS-mutant LUAD cells by lentiviral or retroviral transductions of specific vectors. Cell viability was assessed by cell proliferation and colony formation assays. PD-L1 expression and apoptosis were measured by flow cytometry. The anti-tumor efficacy of the combined treatment with trametinib and PD-1 blockade was investigated in KRAS-mutant LUAD mouse models, and the effects on the tumor immune infiltrate were analyzed by flow cytometry and immunohistochemistry.

RESULTS

We found that trametinib activates the proteasome-ubiquitin system to downregulate Id1 in KRAS-mutant LUAD tumors. Moreover, we found that Id1 plays a major role in the acquired resistance to trametinib treatment in KRAS-mutant LUAD cells. Using two preclinical syngeneic KRAS-mutant LUAD mouse models, we found that trametinib synergizes with PD-1/PD-L1 blockade to hamper lung cancer progression and increase survival. This anti-tumor activity depended on trametinib-mediated Id1 reduction and was associated with a less immunosuppressive tumor microenvironment and increased PD-L1 expression on tumor cells.

CONCLUSIONS

Our data demonstrate that Id1 expression is involved in the resistance to trametinib and in the synergistic effect of trametinib with anti-PD-1 therapy in KRAS-mutant LUAD tumors. These findings suggest a potential therapeutic approach for immunotherapy-refractory KRAS-mutant lung cancers.

Vincristine Enhances the Efficacy of MEK Inhibitors in Preclinical Models of KRAS-mutant Colorectal Cancer

Mutations in KRAS are found in more than 50% of tumors from patients with metastatic colorectal cancer (mCRC). However, direct targeting of most KRAS mutations is difficult; even the recently developed KRASG12C inhibitors failed to show significant benefit in patients with mCRC. Single agents targeting mitogen-activated protein kinase kinase (MEK), a downstream mediator of RAS, have also been ineffective in colorectal cancer. To identify drugs that can enhance the efficacy of MEK inhibitors, we performed unbiased high-throughput screening using colorectal cancer spheroids. We used trametinib as the anchor drug and examined combinations of trametinib with the NCI-approved Oncology Library version 5. The initial screen, and following focused validation screens, identified vincristine as being strongly synergistic with trametinib. In vitro, the combination strongly inhibited cell growth, reduced clonogenic survival, and enhanced apoptosis compared with monotherapies in multiple KRAS-mutant colorectal cancer cell lines. Furthermore, this combination significantly inhibited tumor growth, reduced cell proliferation, and increased apoptosis in multiple KRAS-mutant patient-derived xenograft mouse models. In vivo studies using drug doses that reflect clinically achievable doses demonstrated that the combination was well tolerated by mice. We further determined that the mechanism underlying the synergistic effect of the combination was due to enhanced intracellular accumulation of vincristine associated with MEK inhibition. The combination also significantly decreased p-mTOR levels in vitro, indicating that it inhibits both RAS-RAF-MEK and PI3K-AKT-mTOR survival pathways. Our data thus provide strong evidence that the combination of trametinib and vincristine represents a novel therapeutic option to be studied in clinical trials for patients with KRAS-mutant mCRC.

SIGNIFICANCE

Our unbiased preclinical studies have identified vincristine as an effective combination partner for the MEK inhibitor trametinib and provide a novel therapeutic option to be studied in patients with KRAS-mutant colorectal cancer.

Cytotoxicity of combinations of the pan-KRAS SOS1 inhibitor BAY-293 against pancreatic cancer cell lines

KRAS is mutated in approximately 25% of cancer patients and first KRAS G12C-specific inhibitors showed promising responses. Pancreatic cancer has the highest frequency of KRAS mutations but the prevailing KRAS G12D mutation is difficult to target. Inhibition of the GTP exchange factor (GEF) SOS1-KRAS interaction impairs oncogenic signaling independently of the specific KRAS mutations. In general, cell lines exhibiting KRAS mutations show specific alterations in respect to glucose utilization, signal transduction and stress survival. The aim of this investigation was to check the putative synergy of the SOS1 inhibitor BAY-293 with modulators targeting specific vulnerabilities of KRAS-mutated cell lines in vitro. The cytotoxicity of BAY-293 combinations was tested against MIA PaCa-2 (G12C), AsPC1 (G12D) and BxPC3 (KRAS wildtype) cell lines using MTT tests and calculation of the combination indices (CI) according to the Chou-Talalay method. The results show that BAY-293 synergizes with modulators of glucose utilization, inhibitors of the downstream MAPK pathway and several chemotherapeutics in dependence of the specific KRAS status of the cell lines. In particular, divergent responses for BAY-293 combinations between pancreatic and NSCLC cell lines were observed for linsitinib, superior inhibitory effects of trametinib and PD98059 in NSCLC, and lack of activity with doxorubicin in case of the pancreatic cell lines. Phosphoproteome analysis revealed inhibition of distinct signaling pathways by BAY-293 for MIA PaCa-2 on the one hand and for Aspc1 and BH1362 on the other hand. In conclusion, BAY-293 exhibits synergy with drugs in dependence of the tumor type and specific KRAS mutation.

Cytotoxicity of combinations of the pan-KRAS inhibitor BAY-293 against primary non-small lung cancer cells

KRAS is mutated in approximately 25% of Non-small Cell Lung Cancer (NSCLC) patients and first specific inhibitors showed promising responses that may be improved by concurrent interference with downstream signaling pathways. Cell lines exhibiting KRAS mutations show specific sensitivities to modulators affecting glucose utilization, signal transduction and cell survival. Novel SOS1-directed inhibitors with a broader anticancer coverage such as BAY-293 and BI-3406 inhibit KRAS through the hindrance of SOS1-KRAS interactions. The aim of this study was to check the putative synergy of BAY-293 with modulators having revealed specific vulnerabilities of KRAS-mutated cell lines. The present investigation tested the cytotoxicity of BAY-293 combinations against a series of Osimertinib-resistant primary NSCLC cell lines using MTT tests and calculation of combination indices according to the Chou-Talalay method. The results show that BAY-293 synergizes with modulators of glucose metabolism, inhibitors of cellular proliferation, several chemotherapeutics and a range of diverse modulators, thus corroborating the chemosensitivities of cells expressing mutated KRAS. In conclusion, BAY-293 exerts cytotoxicity with a wide range of drugs against Osimertinib-resistant primary NSCLC cell lines. The administration of pan-KRAS inhibitors alone may be limited in vivo by toxicity to normal tissues but made feasible by its use as part of suitable drug combinations. This study shows that BAY-293 combinations are active against NSCLC cells not further amenable to mutated EGFR-directed targeted therapy and results likewise hold relevance for pancreatic and colon cancer.

Pan-RAS inhibitors: Hitting multiple RAS isozymes with one stone

Mutations in the three RAS oncogenes are present in approximately 30% of all human cancers that drive tumor growth and metastasis by aberrant activation of RAS-mediated signaling. Despite the well-established role of RAS in tumorigenesis, past efforts to develop small molecule inhibitors have failed for various reasons leading many to consider RAS as "undruggable." Advances over the past decade with KRAS(G12C) mutation-specific inhibitors have culminated in the first FDA-approved RAS drug, sotorasib. However, the patient population that stands to benefit from KRAS(G12C) inhibitors is inherently limited to those patients harboring KRAS(G12C) mutations. Additionally, both intrinsic and acquired mechanisms of resistance have been reported that indicate allele-specificity may afford disadvantages. For example, the compensatory activation of uninhibited wild-type (WT) NRAS and HRAS isozymes can rescue cancer cells harboring KRAS(G12C) mutations from allele-specific inhibition or the occurrence of other mutations in KRAS. It is therefore prudent to consider alternative drug discovery strategies that may overcome these potential limitations. One such approach is pan-RAS inhibition, whereby all RAS isozymes co-expressed in the tumor cell population are targeted by a single inhibitor to block constitutively activated RAS regardless of the underlying mutation. This chapter provides a review of past and ongoing strategies to develop pan-RAS inhibitors in detail and seeks to outline the trajectory of this promising strategy of RAS inhibition.

Strategies to tackle RAS-mutated metastatic colorectal cancer

The RAS oncogene is among the most commonly mutated in cancer. RAS mutations are identified in about half of patients diagnosed with metastatic colorectal cancer (mCRC), conferring poor prognosis and lack of response to anti-epidermal growth factor receptor (EGFR) antibodies. In the last decades, several investigational attempts failed in directly targeting RAS mutations, thus RAS was historically regarded as 'undruggable'. Recently, novel specific KRASG12C inhibitors showed promising results in different solid tumors, including mCRC, renewing interest in this biomarker as a target. In this review, we discuss different strategies of RAS targeting in mCRC, according to literature data in both clinical and preclinical settings. We recognized five main strategies focusing on those more promising: direct RAS targeting, targeting the mitogen-activated protein kinase (MAPK) pathway, harnessing RAS through immunotherapy combinations, RAS targeting through metabolic pathways, and finally other miscellaneous approaches. Direct KRASG12C inhibition is emerging as the most promising strategy in mCRC as well as in other solid malignancies. However, despite good disease control rates, tumor response and duration of response are still limited in mCRC. At this regard, combinational approaches with anti-epidermal growth factor receptor drugs or checkpoint inhibitors have been proposed to enhance treatment efficacy, based on encouraging results achieved in preclinical studies. Besides, concomitant therapies increasing metabolic stress are currently under evaluation and expected to also provide remarkable results in RAS codon mutations apart from KRASG12C. In conclusion, based on hereby reported efforts of translational research, RAS mutations should no longer be regarded as 'undruggable' and future avenues are now opening for translation in the clinic in mCRC.

Senescence-Induced Vascular Remodeling Creates Therapeutic Vulnerabilities in Pancreas Cancer

KRAS mutant pancreatic ductal adenocarcinoma (PDAC) is characterized by a desmoplastic response that promotes hypovascularity, immunosuppression, and resistance to chemo- and immunotherapies. We show that a combination of MEK and CDK4/6 inhibitors that target KRAS-directed oncogenic signaling can suppress PDAC proliferation through induction of retinoblastoma (RB) protein-mediated senescence. In preclinical mouse models of PDAC, this senescence-inducing therapy produces a senescence-associated secretory phenotype (SASP) that includes pro-angiogenic factors that promote tumor vascularization, which in turn enhances drug delivery and efficacy of cytotoxic gemcitabine chemotherapy. In addition, SASP-mediated endothelial cell activation stimulates the accumulation of CD8⁺ T cells into otherwise immunologically "cold" tumors, sensitizing tumors to PD-1 checkpoint blockade. Therefore, in PDAC models, therapy-induced senescence can establish emergent susceptibilities to otherwise ineffective chemo- and immunotherapies through SASP-dependent effects on the tumor vasculature and immune system.

Neuroendocrine regulation of cholangiocarcinoma: A status quo review

Increasing studies have demonstrated that neuroendocrine system is involved in the development and progression of cholangiocarcinoma. The neuroendocrine hormones, neurotransmitters and neuropeptides regulate cholangiocarcinoma via affecting pathophysiology of tumor cells. The developing interaction and interplay between neuroendocrine-associated factors and tumor cells provide novel insights into neural control of tumorigenesis and reveal potential therapeutic effect on patients with cholangiocarcinoma. Herein we reviewed the latest findings and achievements which demonstrate the close interactions between neuroendocrine regulation and progression of cholangiocarcinoma. Also, future therapeutic approaches targeting neuroendocrine-associated factors are discussed which may help improve management and treatment of cholangiocarcinoma.

Therapeutic strategies to target RAS-mutant cancers

RAS genes are the most commonly mutated oncogenes in cancer, but effective therapeutic strategies to target RAS-mutant cancers have proved elusive. A key aspect of this challenge is the fact that direct inhibition of RAS proteins has proved difficult, leading researchers to test numerous alternative strategies aimed at exploiting RAS-related vulnerabilities or targeting RAS effectors. In the past few years, we have witnessed renewed efforts to target RAS directly, with several promising strategies being tested in clinical trials at different stages of completion. Important advances have also been made in approaches designed to indirectly target RAS by improving inhibition of RAS effectors, exploiting synthetic lethal interactions or metabolic dependencies, using therapeutic combination strategies or harnessing the immune system. In this Review, we describe historical and ongoing efforts to target RAS-mutant cancers and outline the current therapeutic landscape in the collective quest to overcome the effects of this crucial oncogene.

Combined MEK and BCL-2/XL Inhibition Is Effective in High-Grade Serous Ovarian Cancer Patient-Derived Xenograft Models and BIM Levels Are Predictive of Responsiveness

Most patients with late-stage high-grade serous ovarian cancer (HGSOC) initially respond to chemotherapy but inevitably relapse and develop resistance, highlighting the need for novel therapies to improve patient outcomes. The MEK/ERK pathway is activated in a large subset of HGSOC, making it an attractive therapeutic target. Here, we systematically evaluated the extent of MEK/ERK pathway activation and efficacy of pathway inhibition in a large panel of well-annotated HGSOC patient-derived xenograft models. The vast majority of models were nonresponsive to the MEK inhibitor cobimetinib (GDC-0973) despite effective pathway inhibition. Proteomic analyses of adaptive responses to GDC-0973 revealed that GDC-0973 upregulated the proapoptotic protein BIM, thus priming the cells for apoptosis regulated by BCL2-family proteins. Indeed, combination of both MEK inhibitor and dual BCL-2/XL inhibitor (ABT-263) significantly reduced cell number, increased cell death, and displayed synergy in vitro in most models. In vivo, GDC-0973 and ABT-263 combination was well tolerated and resulted in greater tumor growth inhibition than single agents. Detailed proteomic and correlation analyses identified two subsets of responsive models-those with high BIM at baseline that was increased with MEK inhibition and those with low basal BIM and high pERK levels. Models with low BIM and low pERK were nonresponsive. Our findings demonstrate that combined MEK and BCL-2/XL inhibition has therapeutic activity in HGSOC models and provide a mechanistic rationale for the clinical evaluation of this drug combination as well as the assessment of the extent to which BIM and/or pERK levels predict drug combination effectiveness in chemoresistant HGSOC.

The Combination of MEK Inhibitor With Immunomodulatory Antibodies Targeting Programmed Death 1 and Programmed Death Ligand 1 Results in Prolonged Survival in Kras/p53-Driven Lung Cancer

INTRODUCTION

This study aimed to characterize the tumor-infiltrating immune cells population in Kras/tumor protein 53 (Trp53)-driven lung tumors and to evaluate the combinatorial antitumor effect with MEK inhibitor (MEKi), trametinib, and immunomodulatory monoclonal antibodies (mAbs) targeting either programmed death -1 (PD-1) or programmed cell death ligand 1 (PD-L1) in vivo.

METHODS

Trp53^FloxFlox;Kras^G12D/+;Rosa26^{LSL-Luciferase/LSL-Luciferase} (PKL) genetically engineered mice were used to develop autochthonous lung tumors with intratracheal delivery of adenoviral Cre recombinase. Using these tumor-bearing lungs, tumor-infiltrating immune cells were characterized by both mass cytometry and flow cytometry. PKL-mediated immunocompetent syngeneic and transgenic lung cancer mouse models were treated with MEKi alone as well as in combination with either anti-PD-1 or anti-PD-L1 mAbs. Tumor growth and survival outcome were assessed. Finally, immune cell populations within spleens and tumors were evaluated by flow cytometry and immunohistochemistry.

RESULTS

Myeloid-derived suppressor cells (MDSCs) were significantly augmented in PKL-driven lung tumors compared to normal lungs of tumor-free mice. PD-L1 expression appeared to be highly positive in both lung tumor cells and, particularly MDSCs. The combinatory administration of MEKi with either anti-PD-1 or anti-PD-L1 mAbs synergistically increased antitumor response and survival outcome compared with single-agent therapy in both the PKL-mediated syngeneic and transgenic lung cancer models. Theses combinational treatments resulted in significant increases of tumor-infiltrating CD8⁺ and CD4⁺ T cells, whereas attenuation of CD11b⁺/Gr-1^high MDSCs, in particular, Ly6G^high polymorphonuclear-MDSCs in the syngeneic model.

CONCLUSIONS

These findings suggest a potential therapeutic approach for untargetable Kras/p53-driven lung cancers with synergy between targeted therapy using MEKi and immunotherapies.

A benzoxazole compound as a novel MEK inhibitor for the treatment of RAS/RAF mutant cancer

Mutations in RAS/RAF occur in large portion of malignancies and are associated with aggressive clinical behaviors and poor prognosis. Therefore, we developed a novel benzoxazole compound (KZ-001) as a highly potent and selective MEK 1/2 inhibitor. Our efforts were focused on enhancing the activity of the known MEK inhibitor AZD6244 and overcoming the shortcomings existing in current MEK inhibitors. Here we show that compound KZ-001 exhibits approximately 30-fold greater inhibition against BRAF- and KRAS-mutant tumor cells than that of AZD6244. These results were also demonstrated using in vivo xenograft models. Furthermore, pharmacokinetics (PK) analysis was performed for KZ-001, and this compound showed good orally bioavailability (28%) and exposure (AUC_0-∞ = 337 ± 169 ng h/mL). To determine its potential clinical application, the synergistic effect of KZ-001 with other agents was investigated both in vitro and in vivo (xenograft models). KZ-001 exhibited synergistic anti-cancer effect in combination with BRAF inhibitor vemurafenib and a microtubule-stabilizing chemotherapeutic agent docetaxel. In addition, KZ-001 inhibited the MAPK pathway like known MEK inhibitors. In summary, KZ-001, a structurally novel benzoxazole compound, was developed as a MEK inhibitor that has potential for cancer treatment.

Ubiquitin-independent, Proteasome-mediated targeted degradation of KRAS in pancreatic adenocarcinoma cells using an engineered ornithine decarboxylase/antizyme system

The oncogene KRAS not only promotes the tumorigenesis of pancreatic cancers but also is required for the malignant progression and metastasis of these cancers. Many methods have been explored to influence the malignant biological behavior of these cancers by targeting mutant KRAS. The ornithine decarboxylase/antizyme (ODC/AZ) system is another protein degradation pathway that exists in nature. The formation of an ODC and protein substrate complex through direct combination can promote its degradation by the 26S proteasome without ubiquitination, and this process can be catalyzed by AZ. In this study, we designed and reconstructed a chimeric fusion protein (named RC-ODC). The engineered fusion protein RC-ODC was confirmed to interact with the mutant KRAS oncoprotein in a co-immunoprecipitation assay, and the introduction of both RC-ODC and AZ resulted in degradation of the exogenous and endogenous mutant KRAS oncoprotein at the post-translational level independent of ubiquitination in vitro. Along with a decreased KRAS level, suppression of PANC-1 cell proliferation was detected in vitro and in vivo, and meanwhile downregulation of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) was also observed. Targeted degradation of the KRAS oncoprotein through the ODC/AZ pathway at the post-translational level may reflect a more effective future therapeutic strategy for pancreatic cancer patients. © 2018 The Authors. IUBMB Life published by Wiley Periodicals,Inc. on behalf of International Union of Biochemistry and Molecular Biology, 71(1):57-65, 2019.

Antiangiogenesis and gene aberration-related therapy may improve overall survival in patients with concurrent KRAS and TP53 hotspot mutant cancer

Purpose

Genetic alterations such as activating KRAS and/or inactivating TP53 are thought to be the most common drivers to tumorigenesis. Therefore, we assessed phase I cancer patients with KRAS+/TP53+ mutations.

Results

Approximately 8% of patients referred to phase I clinical trials harbored concurrent KRAS and TP53 mutations. Patients who received a phase I trial therapy (n = 57) had a median OS of 12 months, compared with 4.6 months in those who were not treated (n = 106; p = 0.003). KRAS G13 and TP53 R273 mutations were associated with poor overall survival (OS), while antiangiogenesis and gene aberration-related therapies were associated with prolonged OS. A prognostic model using neutrophilia, thrombocytosis, hypoalbuminemia, body mass index <30 kg/m², and the absence of lung metastasis was established and validated. Phase I cancer patients in the low-risk group had a median OS of 16.6 months compared with 5.4 months in the high-risk group (p < 0.001). Untreated patients in the low-risk group had a median OS of 6.7 months compared with 3.6 months in the high-risk group (p = 0.033).

Experimental Design

We analyzed 163 consecutive patients with advanced KRAS+/TP53+ mutant cancer who were referred to phase I clinical trials, to identify molecular aberrations, clinical characteristics, survivals, and potentially effective treatment regimens.

Conclusions

This study provided preliminary evidence that besides modulation of the proinflammatory state, antiangiogensis and concomitant gene aberration-related therapies may improve the treatment of KRAS+/TP53+ mutant cancer.

Ginsenosides synergize with mitomycin C in combating human non-small cell lung cancer by repressing Rad51-mediated DNA repair

The use of ginseng extract as an adjuvant for cancer treatment has been reported in both animal models and clinical applications, but its molecular mechanisms have not been fully elucidated. Mitomycin C (MMC), an anticancer antibiotic used as a first- or second-line regimen in the treatment for non-small cell lung carcinoma (NSCLC), causes serious adverse reactions when used alone. Here, by using both in vitro and in vivo experiments, we provide evidence for an optimal therapy for NSCLC with total ginsenosides extract (TGS), which significantly enhanced the MMC-induced cytotoxicity against NSCLC A549 and PC-9 cells in vitro when used in combination with relatively low concentrations of MMC. A NSCLC xenograft mouse model was used to confirm the in vivo synergistic effects of the combination of TGS with MMC. Further investigation revealed that TGS could significantly reverse MMC-induced S-phase cell cycle arrest and inhibit Rad51-mediated DNA damage repair, which was evidenced by the inhibitory effects of TGS on the levels of phospho-MEK1/2, phospho-ERK1/2 and Rad51 protein and the translocation of Rad51 from the cytoplasm to the nucleus in response to MMC. In summary, our results demonstrate that TGS could effectively enhance the cytotoxicity of MMC against NSCLC cells in vitro and in vivo, thereby revealing a novel adjuvant anticancer mechanism of TGS. Combined treatment with TGS and MMC can significantly lower the required concentration of MMC and can further reduce the risk of side effects, suggesting a better treatment option for NSCLC patients.

Antitumor Properties of RAF709, a Highly Selective and Potent Inhibitor of RAF Kinase Dimers, in Tumors Driven by Mutant RAS or BRAF

Resistance to the RAF inhibitor vemurafenib arises commonly in melanomas driven by the activated BRAF oncogene. Here, we report antitumor properties of RAF709, a novel ATP-competitive kinase inhibitor with high potency and selectivity against RAF kinases. RAF709 exhibited a mode of RAF inhibition distinct from RAF monomer inhibitors such as vemurafenib, showing equal activity against both RAF monomers and dimers. As a result, RAF709 inhibited MAPK signaling activity in tumor models harboring either BRAF^V600 alterations or mutant N- and KRAS-driven signaling, with minimal paradoxical activation of wild-type RAF. In cell lines and murine xenograft models, RAF709 demonstrated selective antitumor activity in tumor cells harboring BRAF or RAS mutations compared with cells with wild-type BRAF and RAS genes. RAF709 demonstrated a direct pharmacokinetic/pharmacodynamic relationship in in vivo tumor models harboring KRAS mutation. Furthermore, RAF709 elicited regression of primary human tumor-derived xenograft models with BRAF, NRAS, or KRAS mutations with excellent tolerability. Our results support further development of inhibitors like RAF709, which represents a next-generation RAF inhibitor with unique biochemical and cellular properties that enables antitumor activities in RAS-mutant tumors.Significance: In an effort to develop RAF inhibitors with the appropriate pharmacological properties to treat RAS mutant tumors, RAF709, a compound with potency, selectivity, and in vivo properties, was developed that will allow preclinical therapeutic hypothesis testing, but also provide an excellent probe to further unravel the complexities of RAF kinase signaling. Cancer Res; 78(6); 1537-48. ©2018 AACR.

Phellinus linteus Grown on Germinated Brown Rice Increases Cetuximab Sensitivity of KRAS-Mutated Colon Cancer

Colon cancer is one of the most common types of cancer, and it has recently become a leading cause of death worldwide. Among colon cancers, the v-ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutated form is notorious for its non-druggable features. Cetuximab, a monoclonal antibody that binds to the epidermal growth factor receptor, has been introduced as an antitumor therapy; however, secondary resistance and side effects significantly limit its effective use in these cancers. In this study, we prepared Phellinuslinteus on germinated brown rice (PBR) extracts to increase the sensitivity of KRAS-mutated colon cancers to cetuximab. The combined treatment of PBR extract and cetuximab suppressed SW480 cell viability/proliferation, with the cells exhibiting altered cellular morphology and clonogenic potential. AnnexinV–fluorescein isothiocyanate/propidium iodide–stained flow cytometry and Western blotting were performed, and PBR extract combined with cetuximab treatment increased apoptosis of the SW480 cells and suppressed their KRAS protein expression. The potential of PBR as a synergistic anticancer agent was further investigated in a tumor-xenografted mouse model. Tumor growth was significantly suppressed with PBR extract and cetuximab co-treatment. In conclusion, PBR increased the sensitivity of KRAS-mutated colon cancer cells to cetuximab, which indicates the potential use of PBR as a medical food against colon cancer.

Correlation between MEK signature and Ras gene alteration in advanced gastric cancer

MEK inhibitor (selumetinib) is a potent, orally active inhibitor of MAPK/ERK pathway. It is important to develop an accurate and robust method indicative of RAS pathway activity to stratify potential patients who can benefit from selumetinib treatment in gastric cancer (GC). First, we surveyed the sensitivity to selumetinib in a panel of 22 GC cell lines and correlated with MEK signature to selumetinib sensitivity. Next, we analyzed MEK signature via nanostring assay in two Asian cohorts using clinical samples (n = 218) and then performed a correlative analysis with MEK signature status and KRAS genotype in GC. MEK signature was predictive of response of selumetinib in GC cell lines regardless of KRAS mutation status. The proportion of high MEK signature by nanostring assay was 6.9% and the proportion of high MEK signature was significantly higher in KRAS altered group in a Korean cohort. None of PIK3CA altered cases belonged to high MEK signature group. MEK high signature was more prevalent in intestinal type by Lauren classification. The correlation between MEK signature, KRAS alteration and treatment response to selumetinib should be validated in prospective clinical trials.

Litchi seed extract inhibits epidermal growth factor receptor signaling and growth of Two Non-small cell lung carcinoma cells

BACKGROUND

Litchi seeds possess rich amounts of phenolics and have been shown to inhibit proliferation of several types of cancer cells. However, the suppression of EGFR signaling in non-small cell lung cancer (NSCLC) by litchi seed extract (LCSE) has not been fully understood.

METHODS

In this study, the effects of LCSE on EGFR signaling, cell proliferation, the cell cycle and apoptosis in A549 adenocarcinoma cells and NCI- H661 large-cell carcinoma cells were examined.

RESULTS

The results demonstrated that LCSE potently reduced the number of cancer cells and induced growth inhibition, cell-cycle arrest in the G1 or G2/M phase, and apoptotic death in the cellular experiment. Only low cytotoxicity effect was noted in normal lung MRC-5 cells. LCSE also suppressed cyclins and Bcl-2 and elevated Kip1/p27, Bax and caspase 8, 9 and 3 activities, which are closely associated with the downregulation of EGFR and its downstream Akt and Erk-1/-2 signaling.

CONCLUSION

The results implied that LCSE suppressed EGFR signaling and inhibited NSCLC cell growth. This study provided in vitro evidence that LCSE could serve as a potential agent for the adjuvant treatment of NSCLC.

Selumetinib in the treatment of non-small-cell lung cancer

The RAS-RAF-MEK-ERK pathway regulates processes involved in the proliferation and survival of cells. KRAS mutations, prevalent in approximately 30% of patients with non-small-cell lung cancer (NSCLC), result in constitutive activation of the pathway. Selumetinib (AZD6244, ARRY-142886) is a potent and selective inhibitor of MEK1/2 which has demonstrated significant efficacy in combination with docetaxel in patients with KRAS mutant pretreated advanced NSCLC. Several trials in combination with other chemotherapy and targeted therapy regimens in lung cancer are ongoing. We review the development of selumetinib in patients with NSCLC, summarize the pharmacodynamic, pharmacokinetic and tolerability characteristics, and the available clinical trial data to understand the role of selumetinib in the treatment of NSCLC.

Coadministration of Trametinib and Palbociclib Radiosensitizes KRAS-Mutant Non-Small Cell Lung Cancers In Vitro and In Vivo

PURPOSE

To investigate the potential roles that p16 (CDKN2A) and RB activation have in sensitization to MEK inhibitor in resistant KRAS-mutant non-small cell lung cancer cells (NSCLC) in vitro and in vivo.

EXPERIMENTAL DESIGN

Cell viability was measured with MTS assays. Effects of administration of radiation and combination drug treatments were evaluated by clonogenic assay, flow cytometry, and Western blots. DNA repair was assessed using immunofluorescent analysis. Finally, lung cancer xenografts were used to examine in vivo effects of drug treatment and radiation therapy.

RESULTS

In this study, we showed that sensitivity to MEK inhibitor correlated to the RB/p16/CDK4 pathway and knockdown of RB induced resistance in cell lines sensitive to MEK inhibitor. Also, overexpression of p16 and inhibition of CDK4 had the ability to sensitize normally resistant cell lines. Our data indicated that the MEK inhibitor (trametinib, GSK112012) cooperated with the CDK4/6 inhibitor (palbociclib, PD0332991) to strongly reduce cell viability of KRAS-mutant NSCLCs that were resistant to the MEK inhibitor in vitro and in vivo. In addition, we report for the first time that resistance of KRAS-mutant NSCLCs to MEK inhibitor is, at least partly, due to p16 mutation status, and we described a drug combination that efficiently reactivates the RB tumor suppressor pathway to trigger radiosensitizing effects, apoptosis, and cell-cycle arrest.

CONCLUSIONS

Our findings suggest that MEK inhibitor in combination with CDK4/6 inhibitor has significant anti-KRAS-mutant NSCLC activity and radiosensitizing effect in preclinical models, potentially providing a novel therapeutic strategy for patients with advanced KRAS-mutant NSCLCs.

Low mutation percentage of KRAS and BRAF genes in Brazilian anal tumors

Anal cancer is a rare type of digestive tract disease, which has had a crescent incidence in a number of regions. Carcinomas are most frequently found, with squamous cell carcinoma (SCC) comprising ~95% of all anal tumors. The major risk factor for development of this type of tumor is human papillomavirus (HPV) infection. However, previous studies have identified patients with anal cancer that are HPV‑/p16‑and observed that they have a poorer outcome compared with HPV+/p16+ patients. This suggests that molecular profile may drive anal cancer progression. The aim of the present study was to evaluate the mutational status of two important oncogenes, KRAS and BRAF, in a series of anal cancer lesions. Resected tumors of the anal canal (n=43) were evaluated, nine of these were high‑grade squamous intra‑epithelial lesion cases (HSIL), 11 were adenocarcinomas, and 23 SCCs. Direct sequencing of KRAS proto‑oncogene, GTPase (KRAS; codons 12 and 13) and B‑Raf proto‑oncogene, serine/threonine kinase (BRAF; codon 600) was performed and associated with patient clinicopathological and molecular features. There was a trend of poorer prognosis of adenocarcinoma compared with HSIL and SCC. Analysis indicated one SCC patient (2.3%) exhibited a KRAS p.G13D mutation, and one adenocarcinoma patient (2.3%) exhibited a BRAF p.V600E mutation. It was observed that, these mutations are rare in anal tumors, and certain patients may be at a disadvantage using targeted therapies based on KRAS and BRAF mutational status. As there is a low mutation percentage in SCCs, adenocarcinomas and HSIL, there may exist other underlying molecular alterations that result in anal cancer development, which require further elucidation.