Mutant SF3B1 promotes malignancy in PDAC

The splicing factor SF3B1 is recurrently mutated in various tumors, including pancreatic ductal adenocarcinoma (PDAC). The impact of the hotspot mutation SF3B1K700E on the PDAC pathogenesis, however, remains elusive. Here, we demonstrate that Sf3b1K700E alone is insufficient to induce malignant transformation of the murine pancreas, but that it increases aggressiveness of PDAC if it co-occurs with mutated KRAS and p53. We further show that Sf3b1K700E already plays a role during early stages of pancreatic tumor progression and reduces the expression of TGF-β1-responsive epithelial-mesenchymal transition (EMT) genes. Moreover, we found that SF3B1K700E confers resistance to TGF-β1-induced cell death in pancreatic organoids and cell lines, partly mediated through aberrant splicing of Map3k7. Overall, our findings demonstrate that SF3B1K700E acts as an oncogenic driver in PDAC, and suggest that it promotes the progression of early stage tumors by impeding the cellular response to tumor suppressive effects of TGF-β.

Progressive plasticity during colorectal cancer metastasis

Metastasis is the principal cause of cancer death, yet we lack an understanding of metastatic cell states, their relationship to primary tumor states, and the mechanisms by which they transition. In a cohort of biospecimen trios from same-patient normal colon, primary and metastatic colorectal cancer, we show that while primary tumors largely adopt LGR5 + intestinal stem-like states, metastases display progressive plasticity. Loss of intestinal cell states is accompanied by reprogramming into a highly conserved fetal progenitor state, followed by non-canonical differentiation into divergent squamous and neuroendocrine-like states, which is exacerbated by chemotherapy and associated with poor patient survival. Using matched patient-derived organoids, we demonstrate that metastatic cancer cells exhibit greater cell-autonomous multilineage differentiation potential in response to microenvironment cues than their intestinal lineage-restricted primary tumor counterparts. We identify PROX1 as a stabilizer of intestinal lineage in the fetal progenitor state, whose downregulation licenses non-canonical reprogramming.

Circulating tumour cells in gastrointestinal cancers: food for thought?

Gastrointestinal (GI) cancers account for 35% of cancer-related deaths, predominantly due to their ability to spread and generate drug-tolerant metastases. Arising from different locations in the GI system, the majority of metastatic GI malignancies colonise the liver and the lungs. In this context, circulating tumour cells (CTCs) are playing a critical role in the formation of new metastases, and their presence in the blood of patients has been correlated with a poor outcome. In addition to their prognostic utility, prospective targeting of CTCs may represent a novel, yet ambitious strategy in the fight against metastasis. A better understanding of CTC biology, mechanistic underpinnings and weaknesses may facilitate the development of previously underappreciated anti-metastasis approaches. Here, along with related clinical studies, we outline a selection of the literature describing biological features of CTCs with an impact on their metastasis forming ability in different GI cancers.

Abstract 611: Colibactin mutation signatures are associated with a distinct colorectal cancer clinicopathologic phenotype

PURPOSE: Alterations in the gut microbiome contribute to colorectal cancer (CRC) pathogenesis. The genotoxin colibactin, produced by pks+ E. coli, directly binds to DNA, leaving genetic scars at A-T rich motifs that can be identified by whole genome/exome sequencing (WGS/WES) as hexanucleotide mutation signatures SBS28 and SBS41. Here, we investigated whether MSK-IMPACT, a clinical targeted exon capture assay with lower genomic coverage (341-468 cancer associated exons), could be used to identify colibactin mutation signatures (CMS) and provide insight into associated clinicopathologic phenotypes.

METHODS: From an institutional pan-cancer cohort of 36,158 tumors assayed using MSK-IMPACT, we identified 11,864 samples (1,386 CRC) with at least 20 mutations and applied TempoSig, an algorithm which uses maximum likelihood-based extraction of mutational signature proportions. Tumors with at least 10% of all mutations attributed to SBS28/41 were deemed CMS+. Due to the association of POLE mutations and microsatellite instability with distinct phenotypes, we excluded these cases from our analysis.

RESULTS: Consistent with prior reports based on WGS/WES, our MSK-IMPACT TempoSig pipeline identified CMS positivity in multiple cancers, notably gastrointestinal (GI) and head and neck cancers. Ampullary tumors (25%) and GI neuroendocrine tumors (8%) had the highest SBS28 and SBS41 positivity respectively. Among microsatellite stable CRCs, we identified 52 patients with at least one sample positive for SBS28 (N=25) or SBS41 (N=27). Compared with CMS negative tumors, SBS28+ but not SBS41+ tumors had higher chromosomal instability as quantified by fraction of the genome altered by copy number alterations (SBS28+: 33.4% vs. SBS28-: 22.3%, P<.01), lower tumor mutation burden (SBS28+: 7.9/Mb vs. SBS28-: 8.8/Mb, P=.011), and a trend toward younger median age at sampling (57 (IQR 46-66) vs. 61 (IQR 51-70), P=.095). SBS28+ tumors harbored more frequent mutations in DNA damage repair (DDR) genes ATR (7.1 vs. 0.5%, P=.02) and ATM (14.3 vs. 4.1%, P=.03). Overall survival from diagnosis was decreased in patients with SBS28+ compared with SBS41+ tumors (22.0 vs. 43.7 months, P<.07), regardless of initial stage (P<.01). Histopathology revealed increased TILs in 13% of evaluable SBS28+ and 7% of SBS41+ tumors, while RNA FISH using a probe targeting the clbP gene required for colibactin synthesis was negative in all CMS+ samples, suggesting that colibactin mutagenesis is an early event not requiring persistent pks+ E. coli colonization.

CONCLUSIONS: TempoSig enables rigorous identification of colibactin mutation signatures in clinically utilized MSK-IMPACT targeted exon datasets. SBS28+ CRCs are clinically distinct and associated with early onset, poor prognosis and DDR pathway alterations. In ongoing studies, we are investigating the therapeutic implications of these findings.

Citation Format: Melissa A. Lumish, Anisha Luthra, Simran Asawa, Francesco Cambuli, Mark Donoghue, Hyung Jun Woo, Andrea Cercek, Rona Yaeger, Jinru Shia, Francisco Sanchez-Vega, Karuna Ganesh. Colibactin mutation signatures are associated with a distinct colorectal cancer clinicopathologic phenotype [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 611.

PCL-Based Composite Scaffold Matrices for Tissue Engineering Applications

Biomaterial-based scaffolds are important cues in tissue engineering (TE) applications. Recent advances in TE have led to the development of suitable scaffold architecture for various tissue defects. In this narrative review on polycaprolactone (PCL), we have discussed in detail about the synthesis of PCL, various properties and most recent advances of using PCL and PCL blended with either natural or synthetic polymers and ceramic materials for TE applications. Further, various forms of PCL scaffolds such as porous, films and fibrous have been discussed along with the stem cells and their sources employed in various tissue repair strategies. Overall, the present review affords an insight into the properties and applications of PCL in various tissue engineering applications.

Cell membrane coated nanoparticles: next-generation therapeutics

Cell membrane coated nanoparticles (NPs) is a biomimetic strategy developed to engineer therapeutic devices consisting of a NP core coated with membrane derived from natural cells such as erythrocytes, white blood cells, cancer cells, stem cells, platelets or bacterial cells. These biomimetic NPs have gained a lot of attention recently owing to their cell surface mimetic features and tailored nanomaterial characteristics. They have shown strong potential in diagnostic and therapeutic applications including those in drug delivery, immune modulation, vaccination and detoxification. Herein we review the various types of cell membrane coated NPs reported in the literature and the unique strengths of these biomimetic NPs with an emphasis on how these bioinspired camouflage strategies have led to improved therapeutic efficacy. We also highlight the recent progress made by each platform in advancing healthcare and precis the major challenges associated with these NPs.

Bone marrow traffic to regenerating islets induced by streptozotocin injection and partial pancreatectomy in mice

The role of bone marrow (BM)-derived cells in the process of pancreatic islet regeneration remains unclear. The purpose of this study was to determine the role of BM cells in the repair process or regeneration of pancreatic islets in mice using chimeric green fluorescent protein (GFP) expressing BM cells. BM-infused chimeric mice were made diabetic by streptozotocin (STZ) injection or 60% partial pancreatectomy. GFP-positive cells within the islets and pancreas were studied immunohistologically. STZ treatment induced a 10-fold increase in PCNA-positive cells within the islets on day 7 posttreatment. GFP-positive cells increased in number within the islets as well as in the pancreatic parenchyma immediately after STZ injection. The partial pancreatectomy induced 2- to 3-fold increases on day 7 to 28 posttreatment. GFP-positive cells increased in number in pancreatic parenchyma but not within the islets. BM traffic to the pancreas significantly increased in the 2 models inducing islet regeneration. In both models, GFP-positive cells were not positive for antibodies against insulin, glucagon, or somatostatin, but were positive for markers of macrophages or fibroblasts, suggesting their involvement in the initiation of islet regeneration.

Gait initiation in bilateral vestibular loss

OBJECTIVE

Gait initiation is a transient procedure between orthostatic posture and steady-state locomotion and includes anticipatory anteroposterior (AP) and lateral movements. Commands for this task are located in some levels of brain stem, which modulates activity of central pattern generator in the spinal cord. The purpose of this work was to explore the role of the vestibular system in this voluntary stepping.

METHODS

Six patients with chronic bilateral vestibular loss (BVL) were measured by means of a large force plate (70 cm x 120 cm ) and the displacement of the center of pressure (COP) during gait initiation was calculated. Measurement parameters comprised maximum distance (MD), velocity (MV) in the AP and lateral direction as well as for pre-, first- and second-step stages, and the angle of the COP trajectory.

RESULTS

For all stages, BVL patients registered lower values for both MD and MV in the AP direction than did normal subjects. In the lateral direction, however, neither MD nor MV in BVL patients showed any difference from those of normals. The step angle of the COP trajectory was obviously reduced.

CONCLUSION

These results suggest that in the AP direction, the vestibulospinal pathway can influence the locomotor related neural circuits, including the central pattern generator and supraspinal levels, by means of modifying the velocity and step length in order to stabilize the trunk. On the other hand, the control mechanism in the lateral direction may be different from that in the AP direction.

The effects of intense click sounds on velocity storage in optokinetic after-nystagmus

Vestibular evoked myogenic potentials (VEMP) occurring after click stimulation in cervical muscles are thought to be a polysynaptic response of otolith-vestibular nerve origin. In optokinetic after-nystagmus (OKAN) the direction of after-nystagmus changes and slow-phase velocity decreases with head tilt. This phenomenon may be an otolith response to the direction of gravity. We assumed that intense clicks might have some influence on OKAN via the otolith-vestibular nerve. Twelve normal subjects who showed VEMP at 75 dB normal hearing level (nHL) clicks were examined. The OKAN was recorded under four conditions: right monaural, left monaural and binaural stimulation by 75 dB nHL clicks, and absence of click stimulation. Horizontal optokinetic stimulation was applied using stepwise increasing speeds from 30 deg/s to 90 deg/s. Two seconds before the stimulus ended, clicks were sounded. The slow-phase velocity of the recorded electro-nystagmography was manually measured. There was no effect on OKAN with unilateral stimulation but binaural stimulation suppressed it. These results suggest that a velocity storage integrator is influenced by intense clicks via the otolithic area.

Neurotological evaluation of vertical semicircular canal function in inner ear malformation. A case report

A 9-year-old boy with inner ear malformation complained of slight deafness and unsteadiness. CT revealed a normal cochlea despite enlargement of the lateral semicircular canals. The vertical semicircular canals developed more or less normally. The caloric test showed complete canal paresis bilaterally; however, a horizontal rotational stimulus elicited a vestibulo-ocular response, which showed only rightward and downward nystagmus, and their maximal slow-phase velocities were low. In addition, the examination of the vertical semicircular canal function using the head-tilted rotation test revealed a more active response, and the maximal slow-phase velocities were higher than those of a standard horizontal rotational test. These results suggest that the function of the vertical semicircular canal was well preserved and that it may have perceived the horizontal acceleration instead of the lateral semicircular canal.

Computed tomographic findings in peritonsillar abscess and cellulitis

The differentiation of a peritonsillar abscess from peritonsillar cellulitis, although difficult on physical examination, is required in order to determine the appropriate treatment. Peritonsillar cellulitis can be treated with antibiotics alone, while a peritonsillar abscess should be drained. Computed tomography (CT) of the neck is often performed to identify the formation of a deep abscess in the neck, but is rarely used to diagnose peritonsillar infections. We report a patient in whom CT was a useful diagnostic tool for distinguishing peritonsillar abscess from peritonsillar cellulitis.

Use of lactate dehydrogenase to evaluate the anti-viral activity against influenza A virus

The detection of lactate dehydrogenase (LDH) can be used to evaluate efficiently anti-influenza A virus agents. LDH levels in the virus-infected Madin-Darby canine kidney cell cultures were significantly higher than in controls, were in proportion to the degree of virus infection, and corresponded to a decrease in mitochondrial dehydrogenase activity as assayed using a tetrazolium colorimetric assay (MTT method). The EC50 value and cytotoxicity of ribavirin, 3-deazaguanine, pyrazofurin, and carbodine against influenza A virus as measured by the LDH detection method was equivalent to that derived by the MTT method.