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Adding irinotecan to neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer (LARC) increases the pathologic complete response (pCR) rate but brings more toxicities. Robust biomarkers to predict response to irinotecan-based nCRT are extremely necessary for selecting the right patients. Our previous study suggests that patient-derived tumor organoids (PDTOs) sensitivity to chemoradiotherapy matches patient responses. In this study, we investigated whether PDTOs sensitivity to irinotecan can predict complete response (CR) and survival. Eligible patients receiving irinotecan-based nCRT between April 5, 2017 and December 11, 2020 were enrolled in the training cohort (n = 91) for response prediction and survival analysis. Patients receiving nCRT between February 21, 2021 and September 17, 2021 were included in the validation cohort (n = 27). Predictive performances of irinotecan organoid size ratio (OSR) for CR or pCR were evaluated. The irinotecan-sensitive groups had higher response rates compared with the insensitive groups (training cohort: 71.8% vs 24.4%, P

e15598 Background: 5-FU-based regimens are the mainstay treatment for colorectal cancer. However, the limited response rate to 5-FU-based regimens hampered the increase in the treatment efficacy of locally advanced rectal cancer. During the drug screening in the rectal cancer organoid biobank (n = 106), we found out that more than half of the organoids that were resistant to 5-FU monotherapy and sensitive to irinotecan maintained sensitive status to the treatment of 5-FU combined with irinotecan (combination-sensitive), while a quite proportion of them turn to become remarkably resistant to 5-FU plus irinotecan (combination-resistant). Some studies suggested the mechanism of 5-FU-based resistance was associated with the activation of some oncogenic pathways. However, the mechanism of the addition of 5-FU promoting the resistance to irinotecan is still unclear. Methods: To investigate the relationship between the combination-resistant organoids and corresponding patient responses, we collected patient clinical responses and survival outcomes. RNA sequencing and ATAC sequencing were performed to identify differential genes and their enrichment pathways. Moreover, small molecule inhibitors were used to try to reverse the resistance induced by 5-FU. Results: Twenty-one organoids showed sensitivity to irinotecan and resistance to 5-FU. Among them, 8 organoids (38.1%) were combination-resistant and 13 organoids (61.9%) showed sensitivity to combination treatment. Combination-resistant organoids corresponding patients had worse pathologic tumor regression grades (pTRGs) distribution (8/8, 100% had TRGs of 2-3 versus 100% had TRGs of 0-1 in combination-sensitive patients; p < 0.05) and disease-free survival (DFS) rates (HR:11.57, 95% IC:1.025-130.5; p = 0.0047) than patients whose organoids were combination-sensitive. Combination-resistant organoids had higher expression of Ki-67 and CD44 and reduced cleaved-caspase 3 in the combination treatment group and 5-FU group compared with the irinotecan group and control. Furthermore, we identified hedgehog pathway activation after adding 5-FU to irinotecan in combination-resistant organoids through RNA sequencing and ATAC sequencing. GANT-61, an inhibitor of the hedgehog pathway, increased sensitivity to the combination of 5-FU and irinotecan in combination-resistant organoids. Conclusions: We found that organoids which are sensitive to irinotecan turn to become resistant to 5-FU combined with irinotecan. Moreover, corresponding patients had worse responses and a lower DFS rate. The hedgehog pathway is activated in these organoids after the addition of 5-FU to irinotecan, and GANT-61 could reverse the resistance caused by 5-FU. However, more organoid-associated trials with large-scale patients are warranted to reverse the 5-FU-based resistance in the future.

Glioblastoma is the most common form of primary brain tumor. Glioblastoma stem cells play an important role in tumor formation by activation of several signaling pathways. Wnt signaling pathway is one such important pathway which helps cellular differentiation to promote tumor formation in the brain. Glioblastoma remains to be a highly destructive type of tumor despite availability of treatment strategies like surgery, chemotherapy, and radiation. Advances in the field of cancer biology have revolutionized therapy by allowing targeting of tumor-specific molecular deregulation. In this review, we discuss about the significance of glioblastoma stem cells in cancer progression through Wnt signaling pathway and highlight the clinical targets being potentially considered for therapy in glioblastoma.

Glioblastomas (GBMs) and lower-grade gliomas (LGGs) are the most common malignant brain tumors. Despite extensive studies that have suggested that there are differences between the two in terms of clinical profile and treatment, their distinctions on a molecular level had not been systematically analyzed. Here, we investigated the distinctions between GBM and LGG based on multidimensional data, including somatic mutations, somatic copy number variants (SCNVs), gene expression, lncRNA expression and DNA methylation levels. We found that GBM patients had a higher mutation frequency and SCNVs than LGG patients. Differential mRNAs and lncRNAs between GBM and LGG were identified and a differential mRNA-lncRNA network was constructed and analyzed. We also discovered some differential DNA methylation sites could distinguish between GBM and LGG samples. Finally, we identified some key GBM- and LGG-specific genes featuring multiple-level molecular alterations. These specific genes participate in diverse functions; moreover, GBM-specific genes are enriched in the glioma pathway. Overall, our studies explored the distinctions between GMB and LGG using a comprehensive genomics approach that may provide novel insights into studying the mechanism and treatment of brain tumors.