Dynamic ctDNA-based analysis of drug-resistant gene alterations at RAS/BRAF wild-type metastatic colorectal cancer patients after cetuximab plus chemotherapy as the first-line treatment.

BACKGROUND: The purpose of this study was to explore the dynamic changes of genomic mutations and their correlations with the efficacy in metastatic colorectal cancer (mCRC) patients treated with cetuximab plus mFOLFOX as the first-line treatment. METHODS: We included mCRC patients from January 2018 to October 2020 as a studied cohort which were treated with cetuximab plus mFOLFOX as first line therapy. Blood samples were collected for circulating tumor DNA (ctDNA) test at three timepoints: before the first-line therapy(baseline), at the time of first-line progression and at the time of second-line progression. Progression-free survival was considered as the primary endpoint while objective response rate and overall survival were determined as the secondary endpoints. RESULTS: Totally 39 patients received first-line treatment, of which 25 patients entered the second-line treatment, while 10 patients entered the third-line treatment. The median follow-up time was 16.4 months (95 %CI, 14.8-19.3). Along the treatment from first-line progress disease (PD) to second-line PD, proportions of TP53 (12/18, 67 %), APC (10/18, 56 %), FBXW7 (3/18, 17 %), and AMER1 (2/18, 11 %) were gradually increased according to results of single nucleotide variation (SNV). CONCLUSIONS: Resistant gene mutations caused by anti-EGFR drugs in RAS/BRAF wild-type mCRC patients can be observed by dynamic ctDNA analysis. TP53 and AMER1 mutations, tumor mutational burden (TMB) levels, and TP53/AMER1 co-mutation may predict the efficacy of the first-line cetuximab-contained treatment. Situations of genetic mutations were differentiated from first-line PD to second-line PD, which indicated that mutation detection may contribute to predict prognosis of mCRC patients.

Noninvasive Imaging of Ras Activity by Monomolecular Biosensor Based on Split-Luciferase Complementary Assay.

Deregulated activity of Ras GTPases has been observed in many types of human cancers, and contributes to the diverse aspects of carcinogenesis. Although the significance in tumorigenesis has been widely accepted and many therapeutic drugs are under development, little attention has been dedicated to the development of sensors for the Ras activity in vivo. Therefore, based on the split firefly luciferase complementation strategy, we developed a monomolecular bioluminescent biosensor to image endogenous Ras activity in living subject. In this biosensor, two inactive luciferase fragments are sandwiched by Raf-1, whose conformation changes upon GTP-Ras binding. Thus, the Ras activity can be surrogated by the intensity of the complementary luciferase. The bioluminescence analyses demonstrated that this novel biosensor behaved the robust and sensitive reporting efficiency in response to the dynamical changes of Ras activity, both in living colorectal cancer cells and in vivo. Compared to the traditional method, such as the pull-down assay, the bioluminescent sensor is simply, noninvasive, faster and more sensitive for the analysis of the endogenous Ras activity. This innovative work opens up the way for monitoring the preclinical curative effect and high-throughput screening of therapeutic drugs targeting Ras pathways.

[The effect of eukaryotic expression plasmid ARHI on gastric cancer].

OBJECTIVE: To study the effect of expressed aplasia ras homolog member I (ARHI) on the malignant biological behaviors of gastric cancer including the proliferation, migration and invasion of the cell. METHODS: The eukaryotic expression plasmid of ARHI was constructed and transfected into MKN-28 cell with lipofectamine 2000 as pEGFP-ARHI group, transfected with pEGFP-N1 as pEGFP-N1 group, and untreated MKN-28 as control group. The expression of ARHI was detected by Western blotting and fluorescence microscope. CCK-8 assay was used to analyze the cell proliferation, the wound-healing assay and transwell assay were performed to investigate the effects on migration and invasion. RESULTS: Compared with the pEGFP-N1 group and control group, proliferation, invasion and migration of the pEGFP-ARHI group were depressed (P < 0.05). CONCLUSION: Recombination eukaryotic expression pEGFP-ARHI could partially reverse the malignant phenotypes of gastric cancer cell MKN-28.