Abstract 88: Autophagy inhibition sensitizes liver kinase b1 (LKB1)-deficient kras-driven lung tumors to MEK inhibitor trametinib

Tumor suppressor Liver Kinase B1 (LKB1) activates 5'-adenosine monophosphate protein kinase (AMPK) and maintains energy homeostasis in response to energy crises. LKB1 and KRAS are the third most frequent co-mutations detected in non-small cell lung cancer (NSCLC), causing aggressive tumor growth, metastases, and resistance to standard chemotherapy as well as immunotherapy. Thus, identifying a novel treatment for patients harboring co-mutations in LKB1 and KRAS is urgently needed. Autophagy degrades and recycles the building blocks for cancer cells to survival metabolic challenges. Using genetically engineered mouse models (GEMMs), we have previously demonstrated that autophagy compensates for Lkb1 loss for KRAS-driven lung tumorigenesis; loss of an autophagy-essential gene Atg7 dramatically impaired tumor initiation and tumor growth in KrasG12D/+;Lkb1-/- (KL) lung tumors. This is in sharp contrast to Lkb1 wild-type (WT) (KrasG12D/+;p53-/- (KP)) tumors that are less sensitive to autophagy gene ablation. To further value our discoveries in clinical translational ability, we treated mouse lung tumor-derived cell lines (TDCLs) with FDA-approved autophagy inhibitor hydroxychloroquine (HCQ) and found that KL TDCLs were much sensitive to HCQ-induced cell death compared with KP TDCLs. Furthermore, a combination treatment of HCQ with mitogen-activated protein kinase kinase (MAPKK or MEK) inhibitor Trametinib showed synergistic anti-proliferative effects in KL TDCLs, but not in KP TDCLs. To elucidate the underlying mechanism of the increased sensitivity of KL TDCLs to Trametinib by autophagy ablation, we performed metabolomic profiling of KL TDCLs with Trametinib, HCQ, or combination treatment. We found that several glycolytic and TCA cycle intermediates, amino acids, and ATP levels were significantly upregulated upon treatment with Trametinib, which were significantly reduced by the combination treatment. Also, the combination treatment significantly reduced the mitochondrial membrane potential, basal respiration, and ATP production in the KL TDCLs compared with the single agents. However, these effects were not observed in KP TDCLs. Similarly, we found that LKB1-mutant human lung cancer cell lines were much more sensitive to the combination treatment than LKB1 WT cells. Finally, we performed in vivo tumor assay using allograft mouse models and GEMMs to validate our in vitro observations. We found anti-tumor synergistic effects of the combination treatment in KL tumor growth, with no such effect in KP tumor growth. Taken together, our observation suggests that autophagy upregulation in Lkb1-deficient tumors cause resistance to Trametinib treatment by maintaining energy homeostasis for cell survival. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1-deficient NSCLC.

Citation Format: Vrushank Dharmesh Bhatt, Taijin Lan, Wenping Wang, Khoosheh Khayati, Eduardo Cararo-Lopes, Jianming Wang, Jerry Kong, Akash Raju, Xuefei Luo, Wenwei Hu, Xiaoyang Su, Eileen White, Jessie Yanxiang Guo. Autophagy inhibition sensitizes liver kinase b1 (LKB1)-deficient kras-driven lung tumors to MEK inhibitor trametinib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 88.

Metagenomic analysis of buffalo rumen microbiome: Effect of roughage diet on Dormancy and Sporulation genes

Buffalo rumen microbiome experiences a variety of diet stress and represents reservoir of Dormancy and Sporulation genes. However, the information on genomic responses to such conditions is very limited. The Ion Torrent PGM next generation sequencing technology was used to characterize general microbial diversity and the repertoire of microbial genes present, including genes associated with Dormancy and Sporulation in Mehsani buffalo rumen metagenome. The research findings revealed the abundance of bacteria at the domain level and presence of Dormancy and Sporulation genes which were predominantly associated with the Clostridia and Bacilli taxa belonging to the phyla Firmicutes. Genes associated with Sporulation cluster and Sporulation orphans were increased from 50% to 100% roughage treatment, thereby promoting sporulation all along the treatments. The spore germination is observed to be the highest in the 75% roughage treatment both in the liquid and solid rumen fraction samples with respect to the decrease in the values of the genes associated with spore core dehydration, thereby facilitating spore core hydration which is necessary for spore germination.

Comprehensive transcriptome profiling of squamous cell carcinoma of horn in Bos indicus

Squamous cell carcinoma (SCC) of horn is frequently observed in Bos indicus affecting 1% of cattle population and accounting 83.34% of total tumours found. The transcriptome profile of horn cancer (HC) tissue and the matched normal (HN) tissue were analysed by RNA-seq using Roche 454 sequencing. A total of 1 504 900 reads comprising of 612 MB data were used to identify differentially expressed genes using CLC Genomic Workbench. These include up-regulation of KRT6A, KRT6B, KRT6C, KRT14, SFN, KRT84, PI3, COL17A1, ANLN, SERPINB5 and down-regulation of BOLA, SCGB1A1, CXCL17, KRT19, BPIFB1, NR4A1 and TFF3 in HC, which are involved in regulation of gene transcription, cell proliferation, apoptosis, cell survival and metabolic pathways. The qPCR analysis of several targets suggested concordance of gene expression profile with RNA-seq analysis. The present findings would provide basis for further screening of genes and identification of markers for early diagnosis and therapeutic intervention of HC.

Milk microbiome signatures of subclinical mastitis-affected cattle analysed by shotgun sequencing

AIMS

Metagenomic analysis of milk samples collected from Kankrej, Gir (Bos indicus) and crossbred (Bos taurus × B. indicus) cattle harbouring subclinical mastitis was carried out by next-generation sequencing 454 GS-FLX technology to elucidate the microbial community structure of cattle milk.

METHODS AND RESULTS

Milk samples from Kankrej, Gir and crossbred cattle were subjected to metagenomic profiling by pyrosequencing. The Metagenomic analysis produced 63·07, 11·09 and 7·87 million base pairs (Mb) of sequence data, assembled in 264 798, 56 114 and 36 762 sequences with an average read length of 238, 197 and 214 nucleotides in Kankrej, Gir and crossbred cattle, respectively. Phylogenetic and metabolic profiles by the web-based tool MG-RAST revealed that the members of Enterobacteriales were predominant in mastitic milk followed by Pseudomonadales, Bacillales and Lactobacillales. Around 56 different species with varying abundance were detected in the subclinically infected milk. Escherichia coli was found to be the most predominant species in Kankrej and Gir cattle followed by Pseudomonas aeruginosa, Pseudomonas mendocina, Shigella flexneri and Bacillus cereus. In crossbred cattle, Staphylococcus aureus followed by Klebsiella pneumoniae, Staphylococcus epidermidis and E. coli were detected in descending order. Metabolic profiling indicated fluoroquinolones, methicillin, copper, cobalt-zinc-cadmium as the groups of antibiotics and toxic compounds to which the organisms showed resistance. Sequences indicating potential of organisms exhibiting multidrug resistance against antibiotics and resistance to toxic compounds were also present. Interestingly, presence of bacteriophages against Staph. aureus, E. coli, Enterobacter and Yersinia species was also observed.

CONCLUSIONS

The analysis identified potential infectious organisms in mastitis, resistance of organisms to antibiotics and chemical compounds and the natural resistance potential of dairy cows.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings of this study may help in formulating strategies for the prevention and treatment of mastitis in dairy animals and consequently in reducing economic losses incurred because of it.