Iqgap3-Ras axis drives stem cell proliferation in the stomach corpus during homoeostasis and repair

OBJECTIVE

Tissue stem cells are central regulators of organ homoeostasis. We looked for a protein that is exclusively expressed and functionally involved in stem cell activity in rapidly proliferating isthmus stem cells in the stomach corpus.

DESIGN

We uncovered the specific expression of Iqgap3 in proliferating isthmus stem cells through immunofluorescence and in situ hybridisation. We performed lineage tracing and transcriptomic analysis of Iqgap3 +isthmus stem cells with the Iqgap3-2A-tdTomato mouse model. Depletion of Iqgap3 revealed its functional importance in maintenance and proliferation of stem cells. We further studied Iqgap3 expression and the associated gene expression changes during tissue repair after tamoxifen-induced damage. Immunohistochemistry revealed elevated expression of Iqgap3 in proliferating regions of gastric tumours from patient samples.

RESULTS

Iqgap3 is a highly specific marker of proliferating isthmus stem cells during homoeostasis. Iqgap3+isthmus stem cells give rise to major cell types of the corpus unit. Iqgap3 expression is essential for the maintenance of stem potential. The Ras pathway is a critical partner of Iqgap3 in promoting strong proliferation in isthmus stem cells. The robust induction of Iqgap3 expression following tissue damage indicates an active role for Iqgap3 in tissue regeneration.

CONCLUSION

IQGAP3 is a major regulator of stomach epithelial tissue homoeostasis and repair. The upregulation of IQGAP3 in gastric cancer suggests that IQGAP3 plays an important role in cancer cell proliferation.

Multidrug Resistance-Associated Protein 2 (MRP2) Mediated Transport of Oxaliplatin-Derived Platinum in Membrane Vesicles

The platinum-based anticancer drug oxaliplatin is important clinically in cancer treatment. However, the role of multidrug resistance-associated protein 2 (MRP2) in controlling oxaliplatin membrane transport, in vivo handling, toxicity and therapeutic responses is unclear. In the current study, preparations of MRP2-expressing and control membrane vesicles, containing inside-out orientated vesicles, were used to directly characterise the membrane transport of oxaliplatin-derived platinum measured by inductively coupled plasma mass spectrometry. Oxaliplatin inhibited the ATP-dependent accumulation of the model MRP2 fluorescent probe, 5(6)-carboxy-2,'7'-dichlorofluorescein, in MRP2-expressing membrane vesicles. MRP2-expressing membrane vesicles accumulated up to 19-fold more platinum during their incubation with oxaliplatin and ATP as compared to control membrane vesicles and in the absence of ATP. The rate of ATP-dependent MRP2-mediated active transport of oxaliplatin-derived platinum increased non-linearly with increasing oxaliplatin exposure concentration, approaching a plateau value (Vmax) of 2680 pmol Pt/mg protein/10 minutes (95%CI, 2010 to 3360 pmol Pt/mg protein/10 minutes), with the half-maximal platinum accumulation rate (Km) at an oxaliplatin exposure concentration of 301 μM (95% CI, 163 to 438 μM), in accordance with Michaelis-Menten kinetics (r² = 0.954). MRP2 inhibitors (myricetin and MK571) reduced the ATP-dependent accumulation of oxaliplatin-derived platinum in MRP2-expressing membrane vesicles in a concentration-dependent manner. To identify whether oxaliplatin, or perhaps a degradation product, was the likely substrate for this active transport, HPLC studies were undertaken showing that oxaliplatin degraded slowly in membrane vesicle incubation buffer containing chloride ions and glutathione, with approximately 95% remaining intact after a 10 minute incubation time and a degradation half-life of 2.24 hours (95%CI, 2.08 to 2.43 hours). In conclusion, MRP2 mediates the ATP-dependent active membrane transport of oxaliplatin-derived platinum. Intact oxaliplatin and its anionic monochloro oxalate ring-opened intermediate appear likely candidates as substrates for MRP2-mediated transport.

"Worm in the eye": the rationale for treatment of DUSN in south India

AIM

To discuss the rationale for different techniques of treatment for DUSN (diffuse unilateral subacute neuroretinitis) and their effectiveness in two patients from south India.

METHODS

Two rare cases of live worms in DUSN from India are reported, where filarial Brugia malayi is endemic. Both cases presented with progressive unilateral loss of vision with no history of animal contact. They were 40 year old, apparently healthy men. In case 1, the worm (1500-2000 microm) was easy to identify with wriggling movements among crisscrossing diffuse subretinal tracks. The worm was destroyed by a single shot of laser to its advancing end, which was followed by oral steroid to control the inflammation caused by the dead worm. In case 2, the worm was small and difficult to identify. Initially diffuse neuroretinitis was diagnosed and treated with intravenous methylprednisolone and oral corticosteroid. A week later, a small live worm (400-600 microm) was found and subsequently destroyed by laser photocoagulation followed by a combination of anthelminthics.

RESULTS

The patients' vision had improved to 6/60-6/36 from counting fingers after a few weeks.

CONCLUSION

The role of a combination of laser treatment, systemic steroid, and anthelminthics is discussed.

Identification of MRP2 as a targetable factor limiting oxaliplatin accumulation and response in gastrointestinal cancer

Oxaliplatin is important for the clinical treatment of colorectal cancer and other gastrointestinal malignancies, but tumour resistance is limiting. Several oxaliplatin transporters were previously identified but their relative contributions to determining oxaliplatin tumour responses and gastrointestinal tumour cell sensitivity to oxaliplatin remains unclear. We studied clinical associations between tumour expression of oxaliplatin transporter candidate genes and patient response to oxaliplatin, then experimentally verified associations found with MRP2 in models of human gastrointestinal cancer. Among 18 oxaliplatin transporter candidate genes, MRP2 was the only one to be differentially expressed in the tumours of colorectal cancer patients who did or did not respond to FOLFOX chemotherapy. Over-expression of MRP2 (endogenously in HepG2 and PANC-1 cells, or induced by stable transfection of HEK293 cells) decreased oxaliplatin accumulation and cytotoxicity but those deficits were reversed by inhibition of MRP2 with myricetin or siRNA knockdown. Mice bearing subcutaneous HepG2 tumour xenografts were sensitised to oxaliplatin antitumour activity by concurrent myricetin treatment with little or no increase in toxicity. In conclusion, MRP2 limits oxaliplatin accumulation and response in human gastrointestinal cancer. Screening tumour MRP2 expression levels, to select patients for treatment with oxaliplatin-based chemotherapy alone or in combination with a MRP2 inhibitor, could improve treatment outcomes.

Clinical evaluation of automated refraction in anterior chamber pseudophakia

Automated refraction with the Canon RK-1 Autoref keratometer was evaluated in 85 eyes of 85 patients with an anterior chamber intraocular lens implant and a best corrected visual acuity of at least 6/12. Autorefraction readings were obtained in 80 (94%) of these eyes. The agreement between autorefraction and clinical refraction data was 89% for spherical equivalence less than 0.51 dioptres (D), 91% for sphere power less than 0.51 D, 82% for cylinder power less than 0.51 D, and 91% for cylinder axis less than 11 degrees. Autorefraction provides acceptably accurate postoperative refraction values in anterior chamber pseudophakia.

The clinical significance of the branching pattern of the facial nerve in Malaysian subjects

Fine dissection was carried out in 79 facial halves from formalin fixed Malaysian adult cadavers of various races, to trace the extracranial part of the facial nerve and its peripheral branches. The facial nerve trunk, after leaving the stylomastoid foramen was located at a depth of 1 to 2 cm from the skin in the vagino-mastoid angle. It bifurcates at the posterior border of the ramus of the mandible and in 3.8% trifurcation was found. Mean distance of bifurcation from the angle of the mandible was 28.06 mm and 81.0% were within the range of 21 to 35 mm. The branching patterns were classified into six types, and the frequency of occurrence was type I 11.39%, type II 15.9%, type III 34.18%, type IV 18.98%, type V 7.59% and type VI 12.67%. Type I, a classical text book pattern was found to be one of the least common patterns. There is no significant difference in percentage of each type between the present study and that of Koreans, though some differences with Caucasians were noted in three uncommon types. The frontal branch could be outlined between the two diverging lines from the earlobe to the lateral ends of the eyebrow and the highest frontal crease. Posterior to the facial artery, the mandibular branch was seen passing below the inferior border of the mandible in 20%; anterior to the artery, this nerve divides into one to four branches. In almost all the cases, branches to the mentalis and the depressor labii inferioris muscles and infrequently branches to the depressor angular oris were seen below the inferior border of the mandible.(ABSTRACT TRUNCATED AT 250 WORDS)

IQGAP3 signalling mediates intratumoral functional heterogeneity to enhance malignant growth

BACKGROUND

The elevation of IQGAP3 expression in diverse cancers indicates a key role for IQGAP3 in carcinogenesis. Although IQGAP3 was established as a proliferating stomach stem cell factor and a regulator of the RAS-ERK pathway, how it drives cancer growth remains unclear.

OBJECTIVE

We define the function of IQGAP3 in gastric cancer (GC) development and progression.

DESIGN

We studied the phenotypic changes caused by IQGAP3 knockdown in three molecularly diverse GC cell lines by RNA-sequencing. In vivo tumorigenesis and lung metastasis assays corroborated IQGAP3 as a mediator of oncogenic signalling. Spatial analysis was performed to evaluate the intratumoral transcriptional and functional differences between control tumours and IQGAP3 knockdown tumours.

RESULTS

Transcriptomic profiling showed that IQGAP3 inhibition attenuates signal transduction networks, such as KRAS signalling, via phosphorylation blockade. IQGAP3 knockdown was associated with significant inhibition of MEK/ERK signalling-associated growth factors, including TGFβ1, concomitant with gene signatures predictive of impaired tumour microenvironment formation and reduced metastatic potential. Xenografts involving IQGAP3 knockdown cells showed attenuated tumorigenesis and lung metastasis in immunodeficient mice. Accordingly, immunofluorescence staining revealed significant reductions of TGFβ/SMAD signalling and αSMA-positive stromal cells; digital spatial analysis indicated that IQGAP3 is indispensable for the formation of two phenotypically diverse cell subpopulations, which played crucial but distinct roles in promoting oncogenic functions.

CONCLUSION

IQGAP3 knockdown suppressed the RAS-TGFβ signalling crosstalk, leading to a significant reduction of the tumour microenvironment. In particular, IQGAP3 maintains functional heterogeneity of cancer cells to enhance malignant growth. IQGAP3 is thus a highly relevant therapy target in GC.

Protocol for identification and validation of IGF2BP1 target genes in pluripotent human embryonic carcinoma cells

We present a detailed protocol to identify and validate IGF2BP1 target genes in pluripotent human embryonic carcinoma cells (NTERA-2). We first identify the target genes through RNA-immunoprecipitation (RIP) sequencing. We then validate the identified targets through the use of RIP-qPCR assays, determine the m⁶A status of target genes by m⁶A-IP, and perform functional validation by quantifying changes in mRNA or protein expression levels upon knockdown of IGF2BP1 or methyltransferases in NTERA-2. For complete details on the use and execution of this protocol, please refer to Myint et al. (2022).¹.

An assessment of clinical predictors of intracranial head injury identified by computed tomography scan

A prospective study was done during a six-month period on 104 consecutive patients who were seen at the Accident and Emergency (A&E) Department of the UHWI and referred for CT scans of the head within 24 hours of sustaining head injuries. There were 74 (71.1%) males and 30 (28.8%) females. The mean age for females was 40.6 years and 32.4 years for males. Patients were clinically assessed for the presence or absence of vomiting, amnesia, loss of consciousness, bleeding of ear, nose and throat (ENT) and Glasgow Coma score (GCS). Negative predictive values were calculated for each parameter individually as well as the combination of all five. The absence of vomiting, amnesia, "loss of consciousness" (LOC) or ENT bleed had negative predictive values of 68%, 73%, 76% and 61.6% respectively. An assessment of Glasgow Coma Scale (GCS) of 15 had a 77.5% negative predictive value. When the history was indeterminate, the negative predictive values were 19%, 25%, 60% and 18% respectively for vomiting, amnesia, LOC and ENT bleed. When all four clinical indicators were absent in the history and examination and the GCS score 15, the negative predictive value for intracranial injury was 89.4%. In summary, the clinical indicators reviewed, alone or in combination, cannot exclude the presence of intracranial injury.