Acid Sphingomyelinase-Ceramide Induced Vascular Injury Determines Colorectal Cancer Stem Cell Fate.

Background/aims: It is unknown whether cancer stem cells respond differentially to treatment compared with progeny, potentially providing therapeutic vulnerabilities. Our program pioneered use of ultra-high single dose radiotherapy, which cures diverse metastatic diseases at a higher rate (90-95%) than conventional fractionation (~65%). Single dose radiotherapy engages a distinct biology involving microvascular acid sphingomyelinase/ceramide signaling, which, via NADPH oxidase-2-dependent perfusion defects, initiates an adaptive tumor SUMO Stress Response that globally-inactivates homologous recombination repair of double stand breaks, conferring cure.

Colorectal Cancer Develops Inherent Radiosensitivity That Can Be Predicted Using Patient-Derived Organoids.

Unlabelled: Identifying colorectal cancer patient populations responsive to chemotherapy or chemoradiation therapy before surgery remains a challenge. Recently validated mouse protocols for organoid irradiation employ the single hit multi-target (SHMT) algorithm, which yields a single value, the D0, as a measure of inherent tissue radiosensitivity. Here, we translate these protocols to human tissue to evaluate radioresponsiveness of patient-derived organoids (PDO) generated from normal human intestines and rectal tumors of patients undergoing neoadjuvant therapy.

Anti-ceramide single-chain variable fragment mitigates radiation GI syndrome mortality independent of DNA repair.

After 9/11, threat of nuclear attack on American urban centers prompted government agencies to develop medical radiation countermeasures to mitigate hematopoietic acute radiation syndrome (H-ARS) and higher-dose gastrointestinal acute radiation syndrome (GI-ARS) lethality. While repurposing leukemia drugs that enhance bone marrow repopulation successfully treats H-ARS in preclinical models, no mitigator potentially deliverable under mass casualty conditions preserves GI tract. Here, we report generation of an anti-ceramide 6B5 single-chain variable fragment (scFv) and show that s.

Organoids Reveal That Inherent Radiosensitivity of Small and Large Intestinal Stem Cells Determines Organ Sensitivity.

Tissue survival responses to ionizing radiation are nonlinear with dose, rather yielding tissue-specific descending curves that impede straightforward analysis of biologic effects. Apoptotic cell death often occurs at low doses, while at clinically relevant intermediate doses, double-strand break misrepair yields mitotic death that determines outcome. As researchers frequently use a single low dose for experimentation, such strategies may inaccurately depict inherent tissue responses.

Early Colorectal Cancers Provide New Evidence for a Lynch Syndrome-to-CMMRD Phenotypic Continuum.

Lynch syndrome (LS) is the most common hereditary colorectal cancer (CRC) syndrome, caused by heterozygous mutations in the mismatch repair (MMR) genes. Biallelic mutations in these genes lead however, to constitutive mismatch repair deficiency (CMMRD). In this study, we follow the diagnostic journey of a 12-year old patient with CRC, with a clinical phenotype overlapping CMMRD.

Methylation Tolerance-Based Functional Assay to Assess Variants of Unknown Significance in the MLH1 and MSH2 Genes and Identify Patients With Lynch Syndrome.

Background & Aims: Approximately 75% of patients with suspected Lynch syndrome carry variants in MLH1 or MSH2, proteins encoded by these genes are required for DNA mismatch repair (MMR). However, 30% of these are variants of unknown significance (VUS). A assay that measures cell response to the cytotoxic effects of a methylating agent can determine the effects of VUS in MMR genes and identify patients with constitutional MMR-deficiency syndrome.

Single-dose radiotherapy disables tumor cell homologous recombination via ischemia/reperfusion injury.

Tumor cure with conventional fractionated radiotherapy is 65%, dependent on tumor cell-autonomous gradual buildup of DNA double-strand break (DSB) misrepair. Here we report that single-dose radiotherapy (SDRT), a disruptive technique that ablates more than 90% of human cancers, operates a distinct dual-target mechanism, linking acid sphingomyelinase-mediated (ASMase-mediated) microvascular perfusion defects to DNA unrepair in tumor cells to confer tumor cell lethality. ASMase-mediated microcirculatory vasoconstriction after SDRT conferred an ischemic stress response within parenchymal tumor cells, with ROS triggering the evolutionarily conserved SUMO stress response, specifically depleting chromatin-associated free SUMO3.

HSP110 T17 simplifies and improves the microsatellite instability testing in patients with colorectal cancer.

Background: Every colorectal cancer (CRC) patient should be tested for microsatellite instability (MSI, a marker for defective DNA mismatch repair) as a first screen for Lynch syndrome (LS). In this study, we investigated whether it may be possible to improve the detection of MSI in CRC. We examined whether the HT17 DNA repeat (critical for correct splicing of the chaperone HSP110) might constitute a superior marker for diagnosis of the MSI phenotype in patients with CRC compared with the standard panel of markers (pentaplex).

Azathioprine induction of tumors with microsatellite instability: risk evaluation using a mouse model.

Mismatch-repair (MMR)-deficient cells show increased in vitro tolerance to thiopurines because they escape apoptosis resulting from MMR-dependent signaling of drug-induced DNA damage. Prolonged treatment with immunosuppressants including azathioprine (Aza), a thiopurine prodrug, has been suggested as a risk factor for the development of late onset leukemias/lymphomas displaying a microsatellite instability (MSI) phenotype, the hallmark of a defective MMR system. We performed a dose effect study in mice to investigate the development of MSI lymphomas associated with long term Aza treatment.

Diagnosis of Constitutional Mismatch Repair-Deficiency Syndrome Based on Microsatellite Instability and Lymphocyte Tolerance to Methylating Agents.

Background & Aims: Patients with bi-allelic germline mutations in mismatch repair (MMR) genes (MLH1, MSH2, MSH6, or PMS2) develop a rare but severe variant of Lynch syndrome called constitutional MMR deficiency (CMMRD). This syndrome is characterized by early-onset colorectal cancers, lymphomas or leukemias, and brain tumors. There is no satisfactory method for diagnosis of CMMRD because screens for mutations in MMR genes are noninformative for 30% of patients.