Combined DNA Analysis from Stool and Blood Samples Improves Tumor Tracking and Assessment of Clonal Heterogeneity in Localized Rectal Cancer Patients.

Objectives: In this study, stool samples were evaluated for tumor mutation analysis via a targeted next generation sequencing (NGS) approach in a small patient cohort suffering from localized rectal cancer. Introduction: Colorectal cancer (CRC) causes the second highest cancer-related death rate worldwide. Thus, improvements in disease assessment and monitoring that may facilitate treatment allocation and allow organ-sparing "watch-and-wait" treatment strategies are highly relevant for a significant number of CRC patients. Methods: Stool-based results were compared with mutation profiles derived from liquid biopsies and the gold standard procedure of tumor biopsy from the same patients. A workflow was established that enables the detection of de-novo tumor mutations in stool samples of CRC patients via ultra-sensitive cell-free tumor DNA target enrichment. Results: Notably, only a 19% overall concordance was found in mutational profiles across the compared sample specimens of stool, tumor, and liquid biopsies. Conclusion: Based on these results, the analysis of stool and liquid biopsy samples can provide important additional information on tumor heterogeneity and potentially on the assessment of minimal residual disease and clonal tumor evolution.

Oncogenic MTOR signaling axis compensates BTK inhibition in a Chronic Lymphocytic Leukemia patient with Richter Transformation: A Case Report and Review of the Literature.

INTRODUCTION: Targeting the B cell receptor (BCR) pathway via ibrutinib, a specific inhibitor of Bruton's tyrosine kinase, has shown marked clinical efficacy in treatment of patients with chronic lymphocytic leukemia (CLL), thus becoming a preferred first line option independent of risk factors. However, acquired resistance to ibrutinib poses a major clinical problem and requires the development of novel treatment combinations to increase efficacy and counteract resistance development and clinical relapse rates. CASE PRESENTATION: In this study, we performed exome and transcriptome analyses of an ibrutinib resistant CLL patient in order to investigate genes and expression patterns associated with ibrutinib resistance. Here we provide evidence that ibrutinib resistance can be attributed to aberrant mammalian target of rapamycin (MTOR) signaling. CONCLUSION: Thus, our study proposes that combined use of MTOR inhibitors with ibrutinib could be a possible option to overcome therapy resistance in ibrutinib treated patients.

Evidence for Non-Cancer-Specific T Cell Exhaustion in the Tcl1 Mouse Model for Chronic Lymphocytic Leukemia.

The reinvigoration of anti-cancer immunity by immune checkpoint therapies has greatly improved cancer treatment. In chronic lymphocytic leukemia (CLL), patients as well as in the Tcl1 mouse model for CLL, PD1-expressing, exhausted T cells significantly expand alongside CLL development; nevertheless, PD1 inhibition has no clinical benefit. Hence, exhausted T cells are either not activatable by simple PD1 blocking in CLL and/or only an insufficient number of exhausted T cells are CLL-specific. In this study, we examined the latter hypothesis by exploiting the Tcl1 transgenic CLL mouse model in combination with TCR transgene expression specific for a non-cancer antigen. Following CLL tumor development, increased PD1 levels were detected on non-CLL specific T cells that seem dependent on the presence of (tumor-) antigen-specific T cells. Transcriptome analysis confirmed a similar exhaustion phenotype of non-CLL specific and endogenous PD1pos T cells. Our results indicate that in the CLL mouse model, a substantial fraction of non-CLL specific T cells becomes exhausted during disease progression in a bystander effect. These findings have important implications for the general efficacy assessment of immune checkpoint therapies in CLL.