Abstract Mucinous Ovarian Carcinoma (MOC) is a rare ovarian cancer histological subtype with distinct pathology, genomics and clinical outcomes compared to other epithelial ovarian cancers. Accordingly, there is little evidence to guide clinical care, particularly in the use of systemic therapies, and the field has lacked informative and diverse pre-clinical models. We developed MOC-specific methods for generating tumour organoids with a success rate of 70% for long-term cultured lines (n=19). Organoid lines were developed from localised, advanced and recurrent tumours, including from biopsy tissue, and represent diverse genomic features not previously captured by existing cell lines. The organoid lines were highly similar to the tumours of origin for genomic and immunohistochemical markers. Screening using a panel of 11 chemotherapy agents highlighted resistance to standard-of-care agents such as carboplatin. Gastrointestinal cancer chemotherapy agents and their combination regimens lacked activity. Paclitaxel was often highly potent at low doses but failed to kill all cells. However, less frequently used drugs such as gemcitabine, topotecan and doxorubicin inhibited many of the lines more effectively than paclitaxel. Available, but non-standard of care, chemotherapy agents should be considered for clinical management of MOC. This is the largest (by ∼10 fold) cohort of fully characterised patient-derived MOC organoid lines described and the first with extensive drug screening data affording an opportunity for drug discovery and screening for personalised treatment.

Abstract The current standard of care for patients presenting with locally advanced rectal cancer is neo-adjuvant chemoradiotherapy (NACRT) followed by total mesorectal excision. Organ preservation as a curative treatment approach for patients with rectal cancer that achieve an excellent response to NACRT is a promising alternative to radical surgery. However, this strategy mandates careful patient selection and its introduction is hampered by heterogenicity between patient responses to therapy. There also exists a lack of standardization between centres in defining the extent of patient responses, leading to difficulties formalizing selection criteria. Novel exploratory models are required to enable appropriate selection of patients that are ideal candidates for organ preservation. Previous tumour models have provided limited clinical utility in mimicking in-vivo patient response profiles and have lacked concordance with patient responses to therapy. Advances in three-dimensional tissue culture techniques have established organoids as an exciting novel preclinical model. Their application into the field of surgical oncology provides a valid individualized model that may enable accurate selection of patients that will benefit from conservative therapy.

BACKGROUND:During the past few decades, the standard of care for locally advanced rectal cancer, involving neoadjuvant chemoradiation followed by surgery, has been associated with a pathological complete response rate of only 10% to 20%. Combination therapy with immune checkpoint inhibitors may improve treatment response. OBJECTIVE:This systematic review examines the current evidence regarding neoadjuvant immune checkpoint inhibitors in locally advanced rectal cancer in terms of treatment efficacy, impact on surgical outcomes, and potential adverse events. DATA SOURCES:A literature search was conducted using the Ovid MEDLINE, Embase, Web of Science, and Cochrane Library databases from the start of database records to October 31, 2024. STUDY SELECTION:All studies that reported outcomes in patients with locally advanced rectal cancer who received immune checkpoint inhibitors as part of their neoadjuvant treatment were included for examination. MAIN OUTCOME MEASURES:Primary outcome was pathological complete response rate. Secondary outcomes were major pathological response rate, clinical complete response rate, complete response rate, R0 resection rate, and sphincter preservation rate. Safety data were included where available. Potential biomarkers of treatment response were identified. RESULTS:Twelve studies were reviewed. All were prospective phase I/II clinical trials. The overall pathological complete response rate ranged from 25% to 62.5% (50% for deficient mismatch repair/high microsatellite instability; 25%-62.5% for proficient mismatch repair/microsatellite stable). The clinical complete response rate ranged from 10.9% to 100% (56%-100% for deficient mismatch repair/high microsatellite instability; 16.4%-48% for proficient mismatch repair/microsatellite stable). The complete response rate ranged from 44% to 75% (75% for deficient mismatch repair/high microsatellite instability; 44%-56.5% for proficient mismatch repair/microsatellite stable). The R0 resection rate ranged from 94% to 100% and the sphincter preservation rate ranged from 59.4% to 100%. The majority of adverse events were of grades 1 and 2. LIMITATIONS:Our review was limited by a small number of mostly single-arm studies with a lack of long-term survival outcomes, as well as marked clinical and methodological heterogeneity among included studies. CONCLUSIONS:Combination therapy with immune checkpoint inhibitors in locally advanced rectal cancer appears to improve treatment response, but high-level evidence and long-term data are still lacking.

A library of potent WEE1 kinase inhibitors was synthesized based on the discontinued frontrunner clinical candidate AZD1775 (1), many of which were more selective for WEE1 over an undesirable off-target of 1, the kinase PLK1. When tested against patient-derived organoids (PDOs) grown from TP53-mutated colorectal cancer (CRC) peritoneal metastases, 34 (IC50 value of 62 nM) exhibited stronger efficacy than 1 (IC50 value of 120 nM) and the best-in-class clinical candidate ZN-c3 (IC50 value of 127 nM). Against primary CRC PDOs with TP53-WT, 34 significantly enhanced DNA damage, replication stress and apoptosis compared to 1, as well as demonstrated high selectivity over patient-matched normal healthy colon PDOs, highlighting a potential therapeutic window for cancer treatment. Overall, this investigation provides critical insight into several potent WEE1 inhibitors that exhibited exceptional efficacy against CRC PDOs and is the first to utilize a PDO platform to assess their effect on healthy and malignant cell viability.

Ssb1 and Ssb2 are single-stranded DNA-binding proteins with overlapping roles in genome stability. Both contain an OB-fold domain and interact with C9orf80 and IntS3, components of the Integrator complex which regulates snRNA processing, enhancer RNA biogenesis, and resolution of promoter-proximal RNA polymerase II (Pol II) pausing or early termination . We previously showed that combined loss of Ssb1 and Ssb2 leads to embryonic lethality or acute multi-organ failure in adult mice. Here, we show that intestine-specific deletion of both genes (DKO) causes severe radiomimetic damage to the intestinal proliferative crypt compartment, resulting in villous atrophy, marked malabsorption, and mortality, demonstrating that gut-specific mSSB loss is sufficient to drive systemic breakdown. An initial surge in intestinal progenitor cell proliferation preceded crypt depletion, suggesting transient regeneration followed by intestinal stem cell (ISC) exhaustion. DKO tissue failed to grow ex vivo , confirming a cell-autonomous requirement for mSsb2 in ISC maintenance. Mechanistically, mSSBs loss led to R-loop accumulation, p53 activation and interferon-stimulated gene expression, consistent with a failure to resolve transcription-associated genomic stress. Together, these findings uncover a critical, previously unrecognized role for Ssb1 and Ssb2 in regulating intestinal stem cell homeostasis and epithelial regeneration, with broad implications for gastrointestinal development, regeneration, and diseases such as cancer and inflammation.

PURPOSE:Long-course chemoradiotherapy (LCCRT) for locally advanced rectal cancer (LARC) achieves a pathologic complete response (pCR) in approximately 10% to 30% of cases. Radiotherapy exerts both immunostimulatory and immunosuppressive effects. Inhibition of PDL1 may augment the immunostimulatory response. We hypothesize that administering avelumab following LCCRT may enhance tumor response and reduce relapse rates. PATIENTS AND METHODS:This was a phase II single-arm trial. Eligible patients had MRI stage T3b to 4/N1 to 2/M0 LARC within 12 cm from the anal verge. Treatment consisted of long-course chemoradiotherapy (LCCRT) with 50.4 Gy and 5-fluorouracil or capecitabine, followed by four cycles of avelumab (10 mg/kg every 2 weeks). Surgical resection was performed 10 to 12 weeks after completion of LCCRT. Fresh tumor biopsies/ctDNA were taken before LCCRT, before avelumab, and at surgery. The primary endpoint was pCR, reported centrally. Secondary endpoints were imaging responses and toxicity, and exploratory endpoints were translational studies (immune evaluation by multiplex IHC and biopsy-derived tumoroids), distant relapse-free survival, and relapse sites. RESULTS:Thirty-seven patients entered the trial, of whom 33 received avelumab and 32 had surgery. The overall response rate by pelvic MRI (N = 33) was 48%. By 2-[¹⁸F]fluoro-2-deoxy-D-glucose PET, there were 10 complete metabolic responses (CMR) and 18 partial metabolic responses (PMR). Regression score 0 (modified Ryan pCR) was observed in 19% of patients (N = 6), and regression score 1 in 16% (N = 5). Overall, 34% of patients (N = 11) had a major pathologic response. Tumors with greater PDL1 expression showed superior pCR/tumor regression. Tumoroid studies indicated intact cellular machinery for PDL1/HLA class-1 expression modulated by IFNγ. No immune-related grade 3 adverse events were observed, and postoperative complications were as expected. The median follow-up was 3.1 years, the 3-year estimated time to progression was 82%, distant relapse-free survival was 80%, and disease-free survival was 80%. CONCLUSIONS:The Ave-Rec phase II study demonstrated that avelumab after LCCRT is deliverable and tolerable, with significant imaging responses and a major pathologic response rate. Tumoral immune cell subsets/checkpoint expression was predictive of pathologic response. The addition of immune checkpoint inhibitors warrants further evaluation in patients with LARC.

Cancers of the central nervous system (CNS) are unique with respect to their tumor microenvironment. Such a status is due to immune-privilege and the cellular behaviors within a highly networked, neural-rich milieu. During tumor development in the CNS, neural, immune and cancer cells establish complex cell-to-cell communication networks which mimic physiological functions, including paracrine signaling and synapse-like formations. This crosstalk regulates diverse pathological functions contributing to tumor progression. In the CNS, regulation of physiological and pathological functions relies on various cell signaling and transcription programs. At the core of these events lies the cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), a master transcriptional regulator in the CNS. CREB is a kinase inducible transcription factor which regulates many CNS functions, including neurogenesis, neuronal survival, neuronal activation and long-term memory. Here, we discuss how CREB-regulated mechanisms operating in diverse cell types, which control development and function of the CNS, are co-opted in CNS tumors.

PDF file - 1974K, Supplementary Figure 2. Antibody against GRP78 protects 4T1.2 cells from BMTP78 but alone has no effect on viability.

Abstract MYB oncogene upregulation is associated with estrogen receptor (ER)-positive breast cancer, but disease requirements for MYB function in vivo have not been explored. In this study, we provide evidence of a critical requirement for MYB functions in models of human and murine breast cancer. In human breast cancer, we found that MYB expression was critical for tumor cell growth both in vitro and in vivo in xenograft settings. In transgenic knockout mice, tissue-specific deletion of the murine MYB gene caused a transient defect in mammary gland development that was reflected in delayed ductal branching and defective apical bud formation. In mouse mammary tumor virus (MMTV)-NEU mice where tumors are initiated by activation of HER2, MYB deletion was sufficient to abolish tumor formation. In the more aggressive MMTV-PyMT model system, MYB deletion delayed tumorigenesis significantly. Together, the findings in these transgenic knockout models implied that MYB was critical during an early window in mammary development when it was essential for tumor initiation, even though MYB loss did not exert a lasting impact upon normal mammary function. Two important MYB-target genes that promote cell survival, BCL2 and GRP78/BIP, were each elevated compared with nontransformed mammary epithelial cells, thereby promoting survival as confirmed in colony formation assays in vitro. Taken together, our findings establish a role for MYB at the hub of ER- and HER2-dependent pathways in mammary carcinogenesis. Cancer Res; 71(22); 7029–37. ©2011 AACR.

Adoption of organoid/tumoroid propagation of normal and malignant intestinal epithelia has provided unparalleled opportunities to compare cell growth factor and signaling dependencies. These 3D structures recapitulate tumours in terms of gene expression regarding the tumor cells but also allow deeper insights into the contribution of the tumour microenvironment (TME). Elements of the TME can be manipulated or added back in the form of infiltrating cytotoxic lymphocytes and/or cancer associated fibroblasts. The effectiveness of chemo-, radio- and immunotherapies can be explored within weeks of deriving these patient-derived tumour avatars informing treatment of these exact patients in a timely manner. Entrenched paths to colorectal cancer (CRC) from the earliest steps of conventional adenoma or serrated lesion formation, and the recognition of further sub-categorisations embodied by consensus-molecular-subtypes (CMS), provide genetic maps allowing a molecular form of pathologic taxonomy. Recent advances in organoid propagation and scRNAseq are reshaping our understanding of CMS and CRC.

PDF file - 998K, Extent of proliferation, MYB and ER expression in wt virgin mammary glands.

PDF file - 89K, Epithelial cell gene expression in tissues employed for the analysis of MYB and A-MYB expression in mammary glands at different stages of development contain epithelial cells.

Supplementary Tables 1-2 from PHLDA1 Expression Marks the Putative Epithelial Stem Cells and Contributes to Intestinal Tumorigenesis

PDF file - 170K, MYB mRNA expression is elevated in mammary tumors and tumor cell lines.

PDF file - 159K, Supplementary Figure 3. BMTP78 kills breast cell lines in a GRP78-dependent manner.

Patient characteristics & analyses.

Supplementary Figure Legends