KRAS Mutant Colorectal Cancer Research Articles

A miR-29b Byproduct Sequence Exhibits Potent Tumor-Suppressive Activities via Inhibition of NF-κB Signaling in KRAS-Mutant Colon Cancer Cells.

We previously demonstrated that miR-29b-3p is a hopeful miRNA-based therapy against colorectal cancer. In this study, we aimed to clarify a value of miR-29b-1-5p as a next-generation treatment, especially for KRAS-mutant colorectal cancer. RT-PCR assay showed that the expression of miR-29b-3p was high, and its partner strand, miR-29b-1-5p, level was only negligible in clinical colorectal cancer samples. Mimic-miR-29b-1-5p significantly inhibited proliferation of KRAS-mutant colorectal cancer cell lines DLD1 and SW480 and KRAS wild-type HT29 cells. Proliferative activity was further examined by either miR-29b-1-5p strand or its opposite complementary sequence because miR-29b-1-5p is a passenger miRNA and may have no physiologic function. We found that completely opposite complementary strand to miR-29b-1-5p, but not miR-29b-1-5p, possessed a potent antitumor effect and named this byproduct miRNA sequence "MIRTX." MIRTX directly targeted the 3'-UTR of CXCR2 and PIK3R1 mRNA and suppressed the NF-κB signaling pathway in KRAS-mutated colorectal cancer cells. MIRTX induced apoptosis in DLD1 with downregulation of antiapoptotic BCL2, BCL-xL, and MCL1 and upregulation of cleaved caspase-3 and cleaved PARP. In mouse xenograft models, systemic administration of MIRTX using a super carbonate apatite as a delivery vehicle significantly inhibited tumor growth of DLD1 and HT29 cells without any particular toxicities. In conclusion, these findings indicate that inhibition of NF-κB signaling by this novel miRNA-based therapeutic could be a promising treatment against refractory KRAS-mutant colorectal cancer and KRAS wild-type colorectal cancer. Mol Cancer Ther; 17(5); 977-87. ©2018 AACR.

One-carbon metabolism biomarkers and genetic variants in relation to colorectal cancer risk by KRAS and BRAF mutation status.

Disturbances in one-carbon metabolism, intracellular reactions involved in nucleotide synthesis and methylation, likely increase the risk of colorectal cancer (CRC). However, results have been inconsistent. To explore whether this inconsistency could be explained by intertumoral heterogeneity, we evaluated a comprehensive panel of one-carbon metabolism biomarkers and some single nucleotide polymorphisms (SNPs) in relation to the risk of molecular subtypes of CRC defined by mutations in the KRAS and BRAF oncogenes. This nested case-control study included 488 CRC cases and 947 matched controls from two population-based cohorts in the Northern Sweden Health and Disease Study. We analyzed 14 biomarkers and 17 SNPs in prediagnostic blood and determined KRAS and BRAF mutation status in tumor tissue. In a multivariate network analysis, no variable displayed a strong association with the risk of specific CRC subtypes. A non-synonymous SNP in the CTH gene, rs1021737, had a stronger association compared with other variables. In subsequent univariate analyses, participants with variant rs1021737 genotype had a decreased risk of KRAS-mutated CRC (OR per allele = 0.72, 95% CI = 0.50, 1.05), and an increased risk of BRAF-mutated CRC (OR per allele = 1.56, 95% CI = 1.07, 2.30), with weak evidence for heterogeneity (Pheterogeneity = 0.01). This subtype-specific SNP association was not replicated in a case-case analysis of 533 CRC cases from The Cancer Genome Atlas (P = 0.85). In conclusion, we found no support for clear subtype-specific roles of one-carbon metabolism biomarkers and SNPs in CRC development, making differences in CRC molecular subtype distributions an unlikely explanation for the varying results on the role of one-carbon metabolism in CRC development across previous studies. Further investigation of the CTH gene in colorectal carcinogenesis with regards to KRAS and BRAF mutations or other molecular characteristics of the tumor may be warranted.

Omega-3 fatty acid DHA modulates p53, survivin, and microRNA-16-1 expression in KRAS-mutant colorectal cancer stem-like cells

BackgroundThe presence of chemotherapy-resistant colorectal cancer stem cells (CCSCs) with KRAS mutation is thought to be one of the primary causes for treatment failure in colorectal cancer (CRC). P53, survivin, and microRNA-16-1 are challenging targets for anticancer drugs which are associated with chemoresistance in CRC. Yet, no p53-, survivin-, and microRNA-16-1-modulating drug with low toxicity but high efficacy against KRAS-mutant CCSCs have been approved for clinical application in CRC. Here, we investigated whether in vitro concentrations of DHA equal to human plasma levels, are able to modulate, Wt-p53, survivin, and microRNA-16-1 in CRC cells with stem cell-like properties.MethodsWt-p53/KRAS-mutant CRC cells (HCT-116) with stem cell-like properties were treated with 100-, 150- and 200-μM/L DHA, after which cell number, viability, growth inhibition, Wt-p53, survivin and microRNA-16-1 expression, caspase-3 activation and apoptotic-rate were evaluated by different cellular and molecular techniques.ResultsAfter 24-, 48-, and 72-h treatments with 100- to 200-μM/L DHA, growth inhibition- rates were measured to be 54.7% to 59.7%, 73.% to 75.8%, and 63.3% to 97.7%, respectively. Treatment for 48 h with indicated DHA concentrations decreased cell number and viability. In addition, we observed a decrease in both the transcript and protein levels of survivin followed by 1.3- to 1.7- and 1.1- to 4.7-fold increases in the Wt-p53 accumulation and caspase-3 activation levels respectively. Treatment with 100 and 150 μM/L DHA increased microRNA-16-1 expression levels by 1.3- to 1.7-fold and enhanced the microRNA-16-1/survivin mRNA, p53/survivin, and caspase-3/survivin protein ratios by 1.7- to 1.8-, 1.3- to 2.6-, and 1.3- to 2-fold increases respectively. A decrease in the number of live cells and an increase in the number of apoptotic cells were also observed with increasing DHA concentrations.ConclusionWt-p53, survivin, and microRNA-16-1 appear to be promising molecular targets of DHA. Thus, DHA might represent an attractive anti-tumor agent directed against KRAS-mutant CCSCs.

The Role of Autophagy and Mitophagy in Synthetic Lethality of KRAS Mutant Human Colorectal Cancer Cells by Phytochemical Formosanin C

Synthetic lethality refers to the interaction between two co‐essential genes such that inhibiting the function of either gene separately results in cell survival, but inhibiting the function of both genes results in cell death. Targeting synthetic lethal interactions may spare normal cells while selectively killing cancer cells. Formosanin C (FC) is an anti‐cancer diosgenin saponin isolated from Paris formosana Hayata (Liliaceae) which is a perennial herb grown in the humid and dark forests of Taiwan at about the level of 1000 m. The plat has been used as a folk remedy for snake‐bite inflammation and tumors. FC is also a component of “Yunnan Bai Yao”, a traditional Chinese hemostatic medicine. Mutation of KRAS, a RAS superfamily of protein, affects the growth and spread of tumors. Nearly 35–45% of colorectal cancer (CRC) has the KRAS mutations which failed to the targeted therapies and led to poor prognosis. Our previous results indicated that FC‐induced apoptosis of human CRC HT‐29 cells (KRAS wild‐type) via the changes of mitochondrial membrane potential. To determine whether FC can benefit CRC with KRAS mutations to overcome cell resistance, HT‐29 and HT‐29 KRAS (with inducible KRAS mutant gene) cells were used in the present study. MTT analysis revealed that FC induced a stronger dosage‐related growth inhibition on HT‐29 KRAS. Annexin V/propidium iodide double staining analysis further showed that both early and late apoptosis were induced to a greater extent by FC on HT‐29 KRAS than HT‐29. No induction of necrosis was observed. FC also induced a higher degree of autophagy on HT‐29 KRAS, characterized by an increase of LC3‐II expression and LC3‐II/I ratio, induction of LC3‐II puncta, and elevation of acidic vesicular organelles (AVOs) formation, representing the production of autolysosomes at the later stage of autophagic flux. It is noteworthy that administration of autophagy inhibitor Bafilomycin A1 increased FC‐induced growth inhibition and elevated apoptosis on both cells, suggesting the FC‐induced autophagy is cytoprotective. Moreover, fluorescence microscopy analysis revealed that FC induced formation of Parkin puncta in HT‐29 KRAS cells to a greater extent. Addition of mitochondrial division inhibitor‐1 (Mdivi‐1), which can selectively inhibit Drp1 to prevent mitochondrial fission and mitophagy, reversed the FC‐induced phenomena. These data suggest that FC‐induced mitophagy was via Drp1 and Parkin pathway. It is noteworthy that addition of the mitophagy inhibitor Mdivi‐1 increased FC‐induced growth inhibition on HT‐29 KRAS, implying that the FC‐induced mitophagy is cytoprotective. Overall, our data indicate that FC may target one more gene other than mutant KRAS to trigger a stronger apoptosis (synthetic lethality), and addition of either autophagy or mitophagy inhibitor further enhanced the FC‐induced cytotoxicity on HT‐29 KRAS cells, suggesting a possible role of autophagy and mitophagy on KRAS mutant CRC.Support or Funding Information(Supported in part by the Ministry of Science and Technology, Taiwan, No. MOST 105‐2320‐B‐003‐003 and National Taiwan Normal University, Taiwan, No. 10502).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Identification of key pathways and genes in mutant KRAS colorectal cancer by integrated bioinformatics analysis.

Identification of key pathways and genes in mutant KRAS colorectal cancer by integrated bioinformatics analysis.

Mutant KRAS promotes liver metastasis of colorectal cancer, in part, by upregulating the MEK-Sp1-DNMT1-miR-137-YB-1-IGF-IR signaling pathway

Although the role of insulin-like growth factor-I receptor (IGF-IR) in promoting colorectal liver metastasis is known, the mechanism by which IGF-IR is upregulated in colorectal cancer (CRC) is not defined. In this study, we obtained evidence that mutant KRAS transcriptionally activates IGF-IR gene expression through Y-box-binding protein (YB)-1 upregulation via a novel MEK-Sp1-DNMT1-miR-137 pathway in CRC cells. The mechanistic link between the tumor suppressive miR-137 and the translational regulation of YB-1 is intriguing because epigenetic silencing of miR-137 represents an early event in colorectal carcinogenesis due to promoter hypermethylation. This proposed signaling axis was further verified by the immunohistochemical evaluations of liver metastases from a cohort of 46 KRAS mutant CRC patients, which showed a significant correlation in the expression levels among Sp1, miR-137, YB-1, and IGF-1R. Moreover, suppression of the expression of YB-1 and IGF-IR via genetic knockdown or the pharmacological inhibition of MEK hampers KRAS-driven colorectal liver metastasis in our animal model studies. From a translational perspective, the identification of this KRAS-driven pathway might provide a mechanistic rationale for the use of a MEK inhibitor as an adjuvant, in combination with standard of care, to prevent the recurrence of colorectal liver metastasis in KRAS mutant CRC patients after receiving liver resection, which warrants further investigation.

75P - Role of p21-activated kinase (PAK) in K-RAS mutant human colorectal cancer models

75P - Role of p21-activated kinase (PAK) in K-RAS mutant human colorectal cancer models

Characterizing heterogeneity in KRAS mutant colorectal cancers (CRC) using cellular, mutation, and immune profiles.

657 Background: Approximately 30%-50% of CRC patients have KRAS mutation, and they are associated with lack of treatment response to anti-EGFR therapy. KRAS mutant CRCs are heterogeneous that not all mutant tumors are dependent on its downstream signaling. At this era of the search for therapeutic targets related to mutant KRAS, it is essential to understand the underlying heterogeneity in KRAS mutant metastatic CRCs with a goal of identifying personalized therapeutic vulnerabilities. To understand KRAS mutation further, in this study we classified KRAS mutant CRCs based on individual cell types in the normal colon crypt and associated them with PIK3CA mutations and interferon-gamma responsive signature. Methods: Publicly available RNAseq gene expression data from KRAS mutant samples were used. Classification of CRC samples into CRCassigner subtypes, KRAS mutation dependents/independent groups, and interferon gamma-responsive status was performed using published signatures. Results: CRC samples (n>200) with KRAS mutant and wild-type statuses were classified into all the five CRCAssigner subtypes (goblet-like, enterocyte, transit-amplifying, stem-like and inflammatory) that represent individual cell types in the normal colon crypt. Interestingly, goblet-like subtype was found to be enriched for KRAS mutation. Among those KRAS mutant CRCs from all the subtypes (n=61), goblet-like samples showed significant enrichment (false discovery rate <0.05; hypergeometric test) for KRAS dependent signature, whereas stem-like subtype showed KRAS independent signature. KRAS independent stem-like CRCs showed increased PIK3CA mutation and expression of interferon-gamma responsive genes compared to dependent CRCs. Conclusions: Overall, KRAS mutant CRCs are heterogeneous with differentiated subtype highly dependent on the mutation and its signalling pathway, whereas less differentiated/stem-like subtype CRCs are independent of the mutation. Also, the enrichment of PIK3CA mutation and interferon-gamma responsive genes mainly in KRAS independent CRC subtype present a potential opportunity to target them using combination immunotherapeutics.

KRAS Mutation and Consensus Molecular Subtypes 2 and 3 Are Independently Associated with Reduced Immune Infiltration and Reactivity in Colorectal Cancer.

Purpose:KRAS mutation is a common canonical mutation in colorectal cancer, found at differing frequencies in all consensus molecular subtypes (CMS). The independent immunobiological impacts of RAS mutation and CMS are unknown. Thus, we explored the immunobiological effects of KRAS mutation across the CMS spectrum.Experimental Design: Expression analysis of immune genes/signatures was performed using The Cancer Genome Atlas (TCGA) RNA-seq and the KFSYSCC microarray datasets. Multivariate analysis included KRAS status, CMS, tumor location, MSI status, and neoantigen load. Protein expression of STAT1, HLA-class II, and CXCL10 was analyzed by digital IHC.Results: The Th1-centric co-ordinate immune response cluster (CIRC) was significantly, albeit modestly, reduced in KRAS-mutant colorectal cancer in both datasets. Cytotoxic T cells, neutrophils, and the IFNγ pathway were suppressed in KRAS-mutant samples. The expressions of STAT1 and CXCL10 were reduced at the mRNA and protein levels. In multivariate analysis, KRAS mutation, CMS2, and CMS3 were independently predictive of reduced CIRC expression. Immune response was heterogeneous across KRAS-mutant colorectal cancer: KRAS-mutant CMS2 samples have the lowest CIRC expression, reduced expression of the IFNγ pathway, STAT1 and CXCL10, and reduced infiltration of cytotoxic cells and neutrophils relative to CMS1 and CMS4 and to KRAS wild-type CMS2 samples in the TCGA. These trends held in the KFSYSCC dataset.Conclusions:KRAS mutation is associated with suppressed Th1/cytotoxic immunity in colorectal cancer, the extent of the effect being modulated by CMS subtype. These results add a novel immunobiological dimension to the biological heterogeneity of colorectal cancer. Clin Cancer Res; 24(1); 224-33. ©2017 AACR.

Involvement of microRNA 27a in a novel Antrodia cinnamomeia inhibits colorectal cancer proliferation, suppresses cancer stem-like phenotype and re-sensitized KRAS mutant colorectal cancer

Involvement of microRNA 27a in a novel Antrodia cinnamomeia inhibits colorectal cancer proliferation, suppresses cancer stem-like phenotype and re-sensitized KRAS mutant colorectal cancer

Review on comparative efficacy of bevacizumab, panitumumab and cetuximab antibody therapy with combination of FOLFOX-4 in KRAS-mutated colorectal cancer patients.

Colorectal cancer, fourth leading form of cancer worldwide and is increasing in alarming rate in the developing countries. Treating colorectal cancer has become a big challenge worldwide and several antibody therapies such as bevacizumab, panitumumab and cetuximab are being used with limited success. Moreover, mutation in KRAS gene which is linked with the colorectal cancer initiation and progression further interferes with the antibody therapies. Considering median progression free survival and overall survival in account, this review focuses to identify the most efficient antibody therapy in combination with chemotherapy (FOLFOX-4) in KRAS mutated colorectal cancer patients. The bevacizumab plus FOLFOX-4 therapy shows about 9.3 months and 8.7 months of progression free survival for KRAS wild and mutant type, respectively. The overall survival is about 34.8 months for wild type whereas for the mutant it is inconclusive for the same therapy. In comparison, panitumumab results in better progression-free survival which is about (9.6 months) and overall survival is about (23.9 months) for the wild type KRAS and the overall survival is about 15.5 months for the mutant KRAS. Cetuximab plus FOLFOX-4 therapy shows about 7.7 months and 5.5 months of progression-free survival for wild type KRAS and mutant type, respectively. Thus, panitumumab shows significant improvement in overall survival rate for wild type KRAS, validating as a cost effective therapeutic for colorectal cancer therapy. This review depicts that panitumumab along with FOLFOX-4 has a higher response in colorectal cancer patients than the either of the two monoclonal antibodies plus FOLFOX-4.

Genome-Wide CRISPR Screen for Essential Cell Growth Mediators in Mutant KRAS Colorectal Cancers.

Targeting mutant KRAS signaling pathways continues to attract attention as a therapeutic strategy for KRAS-driven tumors. In this study, we exploited the power of the CRISPR-Cas9 system to identify genes affecting the tumor xenograft growth of human mutant KRAS (KRASMUT) colorectal cancers. Using pooled lentiviral single-guide RNA libraries, we conducted a genome-wide loss-of-function genetic screen in an isogenic pair of human colorectal cancer cell lines harboring mutant or wild-type KRAS. The screen identified novel and established synthetic enhancers or synthetic lethals for KRASMUT colorectal cancer, including targetable metabolic genes. Notably, genetic disruption or pharmacologic inhibition of the metabolic enzymes NAD kinase or ketohexokinase was growth inhibitory in vivo In addition, the chromatin remodeling protein INO80C was identified as a novel tumor suppressor in KRASMUT colorectal and pancreatic tumor xenografts. Our findings define a novel targetable set of therapeutic targets for KRASMUT tumors. Cancer Res; 77(22); 6330-9. ©2017 AACR.

A Bifunctional MAPK/PI3K Antagonist for Inhibition of Tumor Growth and Metastasis.

Responses to targeted therapies frequently are brief, with patients relapsing with drug-resistant tumors. For oncogenic MEK and BRAF inhibition, drug resistance commonly occurs through activation of PI3K/AKT/mTOR signaling and immune checkpoint modulation, providing a robust molecular target for concomitant therapy. Here, we evaluated the efficacy of a bifunctional kinase inhibitor (ST-162) that concurrently targets MAPK and PI3K signaling pathways. Treatment with ST-162 produced regression of mutant KRAS- or BRAF-addicted xenograft models of colorectal cancer and melanoma and stasis of BRAF/PTEN-mutant melanomas. Combining ST-162 with immune checkpoint blockers further increased efficacy in a syngeneic KRAS-mutant colorectal cancer model. Nascent transcriptome analysis revealed a unique gene set regulated by ST-162 related to melanoma metastasis. Subsequent mouse studies revealed ST-162 was a potent inhibitor of melanoma metastasis to the liver. These findings highlight the significant potential of a single molecule with multikinase activity to achieve tumor control, overcome resistance, and prevent metastases through modulation of interconnected cell signaling pathways. Mol Cancer Ther; 16(11); 2340-50. ©2017 AACR.

Circulating tumor DNA is effective for detection of KRAS mutation in colorectal cancer: a meta-analysis.

Circulating tumor DNA (ctDNA) offers a novel and minimally invasive approach to the detection of the KRAS oncogene mutation in colorectal cancer. This study was conducted to compare the prognostic value of ctDNA with that of the current gold standard tumor tissue analysis. A systematic literature review was conducted to identify relevant articles published from inception to December 27, 2016; the PubMed, Web of Science, Embase, Wanfang and China National Knowledge Infrastructure databases were searched. Pooled specificity, sensitivity, positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio (DOR) estimates and areas under summary receiver operating characteristic (AUSROC) curves were calculated. We also performed subgroup and sensitivity analyses. Twenty-three studies with 1,715 colorectal cancer patients were included. The overall sensitivity and specificity were 0.75 (95% confidence interval [CI], 0.66-0.82) and 0.98 (CI, 0.95-0.99), respectively. The positive likelihood ratio was 31.8 (95% CI, 14.8-68.3), and the negative likelihood ratio was 0.26 (95% CI, 0.19-0.36). In addition, the AUSROC and DOR were 0.96 (95% CI, 0.93-0.97) and 123 (95% CI, 52-291), respectively. Substantial heterogeneity was observed across studies (I² = 95%, 95% CI, 91-99). None of the subgroups investigated, including those defined by blood sample type, study region, TNM stage, detection site and detection method, could indicate the source of the observed heterogeneity. The results of the sensitivity analysis indicated that the results of our meta-analysis were stable. Circulating tumor DNA may serve as a viable alternative to tissue analysis for the detection of KRAS mutations in colorectal cancer.

Patterns and the Occurrence of KRAS Mutations in Metastatic Colorectal Cancers-a Study from Indian Regional Cancer Centre.

Mutation analysis of the KRAS oncogene is established as a predictive biomarker in Colorectal cancer (CRC). Many prospective clinical trials have shown that only CRCs with wild-type KRAS respond to anti-epidermal growth factor receptor (EGFR) treatment. Hence, mutation analysis is mandatory before treatment of metastatic CRCs. There are very few studies on the KRAS mutation status in the Indian setting. Hence, this study was done to document the patterns of KRAS mutations in CRCs reporting to a regional cancer centre in South India. Among 150 cases of metastatic colorectal cancer reporting over a period of 20months, 48 random cases were analyzed for the KRAS mutational status of codons 12 and 13 of the KRAS gene by genomic sequencing. KRAS mutations in codons 12 and 13 were present in 9/48 (18.75%) of all analyzed CRCs. The common types of mutations were glycine to aspartate on codon 12 (p.G12D), glycine to valine on codon 12 (p.G12V), and glycine to aspartate on codon 13 (p.G13D).

LC-MS-based metabolomics revealed SLC25A22 as an essential regulator of aspartate-derived amino acids and polyamines in KRAS-mutant colorectal cancer.

SLC25A22, which encodes the mitochondrial glutamate transporter, is overexpressed in colorectal cancer (CRC) and is essential for the proliferation of CRC cells harboring KRAS mutations. However, the role of SLC25A22 on metabolic regulation in KRAS-mutant CRC cells has not been comprehensively characterized.We performed non-targeted metabolomics, targeted metabolomics and isotope kinetic analysis of KRAS-mutant DLD1 cells with or without SLC25A22 knockdown using ultra-high-performance liquid chromatography (UHPLC) coupled to Orbitrap mass spectrometry (MS) or tandem MS (MS/MS).Global metabolomics analysis identified 35 altered metabolites, which were attributed to alanine, aspartate and glutamate metabolism, urea cycle and polyamine metabolism. Targeted metabolomics including 24 metabolites revealed that most tricarboxylic acid (TCA) cycle intermediates, aspartate-derived asparagine, alanine and ornithine-derived polyamines were strongly down-regulated in SLC25A22 knockdown cells. Moreover, targeted kinetic isotope analysis showed that most of the 13C-labeled ornithine-derived polyamines were significantly decreased in SLC25A22 knockdown cells and culture medium. Exogenous addition of polyamines could significantly promote cell proliferation in DLD1 cells, highlighting their potential role as oncogenic metabolites that function downstream of SLC25A22-mediated glutamine metabolism.Collectively, SLC25A22 acts as an essential metabolic regulator during CRC progression as it promotes the synthesis of aspartate-derived amino acids and polyamines in KRAS mutant CRC cells.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Synergistic activity and heterogeneous acquired resistance of combined MDM2 and MEK inhibition in KRAS mutant cancers.

There are currently no effective targeted therapies for KRAS mutant cancers. Therapeutic strategies that combine MEK inhibitors with agents that target apoptotic pathways may be a promising therapeutic approach. We investigated combining MEK and MDM2 inhibitors as a potential treatment strategy for KRAS mutant non-small cell lung cancers and colorectal carcinomas that harbor wild-type TP53. The combination of pimasertib (MEK inhibitor) + SAR405838 (MDM2 inhibitor) was synergistic and induced the expression of PUMA and BIM, led to apoptosis and growth inhibition in vitro, and tumor regression in vivo. Acquired resistance to the combination commonly resulted from the acquisition of TP53 mutations, conferring complete resistance to MDM2 inhibition. In contrast, resistant clones exhibited marked variability in sensitivity to MEK inhibition, which significantly impacted sensitivity to subsequent treatment with alternative MEK inhibitor-based combination therapies. These results highlight both the potential promise and limitations of combining MEK and MDM2 inhibitors for treatment of KRAS mutant NSCLC and CRC.

Clinical Role of ASCT2 (SLC1A5) in KRAS-Mutated Colorectal Cancer.

Mutation in the KRAS gene induces prominent metabolic changes. We have recently reported that KRAS mutations in colorectal cancer (CRC) cause alterations in amino acid metabolism. However, it remains to be investigated which amino acid transporter can be regulated by mutated KRAS in CRC. Here, we performed a screening of amino acid transporters using quantitative reverse-transcription polymerase chain reaction (RT-PCR) and then identified that ASCT2 (SLC1A5) was up-regulated through KRAS signaling. Next, immunohistochemical analysis of 93 primary CRC specimens revealed that there was a significant correlation between KRAS mutational status and ASCT2 expression. In addition, the expression level of ASCT2 was significantly associated with tumor depth and vascular invasion in KRAS-mutant CRC. Notably, significant growth suppression and elevated apoptosis were observed in KRAS-mutant CRC cells upon SLC1A5-knockdown. ASCT2 is generally known to be a glutamine transporter. Interestingly, SLC1A5-knockdown exhibited a more suppressive effect on cell growth than glutamine depletion. Furthermore, SLC1A5-knockdown also resulted in the suppression of cell migration. These results indicated that ASCT2 (SLC1A5) could be a novel therapeutic target against KRAS-mutant CRC.

Potential Role of Metabolic Intervention in the Management of Advanced Differentiated Thyroid Cancer.

Well-differentiated thyroid carcinoma (DTC) is the most common endocrine malignancy that has an excellent prognosis with a 5-year survival rate of about 98%. However, approximately 50% of the patients with DTC who present with distant metastases (advanced DTC) die from the disease within 5 years of initial diagnosis even after getting the appropriate therapy. Apart from recent advancements in chemotherapy agents, the potential role of metabolic interventions, including the use of metformin, ketogenic diet, and high-dose vitamin C in the management of advanced cancers have been investigated as a less toxic co-adjuvant therapies. The role of vitamin C has been of interest again after a preclinical mice study showed that high-dose vitamin C is selectively lethal to KRAS and BRAF mutant colorectal cancer cells by targeting the glutathione pathway. This raises the possibility of utilizing high-doses of vitamin C in the treatment of aDTC where KRAS and BRAF mutations are common. Similarly, alteration of cellular metabolism by low-carbohydrate ketogenic diets can be an important therapeutic strategy to selectively kill cancer cells that mainly survive on glycolysis. Among the potential adjuvant therapies proposed in this paper, metformin is the only agent that has shown benefit in human model of aDTC, the others have shown benefit but in preclinical/animal studies only and need to be further evaluated in large clinical trials. In conclusion, in addition to concurrent chemotherapy options, these metabolic interventions may have a great potential as co-adjuvant therapy in the management of aDTC.