The Molecular Mechanism Of Antitumor Drug SAHA Resistance And Inducing And Tracking Clonal Mutation With Mosaic Analysis

Genomes are inherently unstable which leads to the variation of DNA sequence and heterogeneity of different cells,some of those mutant cells gain growth advantage and develop to tumor.Heterogeneity is one of the tumor characters which affects the sensitivity to drug treatment.Histone deacetylase inhibitors(HDIs)represent a new class of anticancer drugs.SAHA is one of HDIs and has been approved for(CTCL).However,SAHA is ineffective against solid tumors in many clinical trials.A better the treatment of cutaneous T cell lymphoma understanding of molecular mechanisms of SAHA resistance may provide the basis for improved patient selection and the enhancement of clinical efficacy.Here we find that the high levels of HDAC6 expression are associated with activated K-ras mutant in colon cancer patients.And expressions of HDAC6 and c-myc are increased in fibroblasts transformed with activated K-ras.Surprisingly,we find that activated K-ras transformed cells are more resistant to SAHA inhibition on cell growth and anchorage-independent colony formation.We show that a K-ras inhibitor sensitizes K-ras mutated lung cancer cells to SAHA induced growth inhibition.We also find that mutant K-ras induces HDAC6 expression by a MAPK dependent pathway.Our study suggests that combined treatment with SAHA and K-ras inhibitors may represent an effective strategy to overcome SAHA resistance.Mosaic analysis offers a way to mimic and track the tumorigenesis with mouse model,the study of tumorigenesis will provide the evidence for drug usage in clinical cancer therapy.Mosaic analysis induces somatic mutation in sporadic cells that are simultaneously labeled with specific marker for lineage tracing on the background of otherwise wild type animals.It has great advantage on studying gene function in cell autonomous manner in multicellular organism.Mosaic clones are typically produced through mitotic recombination but this stringent requirement prevents general application of mosaic analysis in mouse genetics.We develop a new mosaic analysis system that can create a couple of conditional knockouts and simultaneously turn on ZsG reen expression in small populations,while mark another small population with wild type genotype as tdTomato which can be taken as internal control in the mosaic analysis.This system can be widely used in the genetic studies because it’s easy to combine with any conditional alleles in mosaic analysis.Here we demonstrate the feasibility of this system in the analysis of Tet2 in clonal expansion of myeloid cell as well as B cell in peripheral blood.At the same time,we take advantage of this system to study Id3 function in intestinal immune cell development and reveal a novel function of Id3 in regulating homeostasis of intestinal macrophages.These studies indicate that the clonal analysis described here offers a practical genetic tool for functional dissection of gene function or multigenic pathways in any tissue types of adut animas.