Introduction

Optical diagnosis (OD) allows real-time endoscopic assessment of polyp histology and holds promise for enhancing colorectal cancer screening. In 2022, ESGE recommended OD performance thresholds for the leave-in-situ strategy (>90% sensitivity/>80% specificity for diminutive polyps in the rectosigmoid) as well as for the resect and discard strategy (>80% sensitivity/>80% specificity for colorectal diminutive adenomas)¹. However, guidance on small polyps (5-9mm) is lacking and it is unknown if high adenoma detection rate (ADR) translates to high OD performance. In Sweden, screening colonoscopies are performed by experienced endoscopists but formal training in OD is not required.

Aims & Methods

This study aimed to evaluate the diagnostic performance of OD for diminutive (<5 mm) and small (5–9 mm) colorectal adenomas, and to assess the relationship between ADR and OD accuracy. Data were retrieved from the Swedish national colorectal cancer screening registry (SveReKKS), including colonoscopies performed between April 2019 and December 2023. Registration of screening colonoscopies is mandatory, but registration of OD is not. Polyps where both OD and histopathology were available were included. Diagnostic performance was assessed using accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for diminutive and small adenomas. Subgroup analyses were performed for rectosigmoid adenomas. ADR was compared between endoscopists who used OD and those who did not. Among endoscopists with >30 OD cases, the correlation of ADR and diagnostic accuracy (measured with Youden's index) was assessed.

Results

Among 12,358 colonoscopies, 24,685 polyps and cancers were identified. OD and histopathological results were available for 3,807 polyps, of which 1,092 were diminutive and 1,460 small polyps. For all diminutive adenomas, OD had 89.0% sensitivity, and 64.0% specificity. In the rectosigmoid, sensitivity was 91.6% and specificity 69.6%. For small adenomas, OD showed 94.4% sensitivity and 76.1% specificity. In the rectosigmoid, sensitivity was very high, 97.1%, but specificity was low, 61.2%. A summary of predictive measures is provided in Table 1. None of the small adenomas falsely diagnosed as non-adenomas by OD harboured high-grade dysplasia or cancer.

Conclusion

In this nationwide screening cohort, OD demonstrated high sensitivity but limited specificity, indicating that leave-in-situ and resect and discard strategies cannot be implemented yet in the Swedish screening program. However, the absence of missed HGD/cancer in small polyps is encouraging, as it indicates abovementioned resection strategies may be considered not only for diminutive adenomas. The absence of a link between high ADR and OD accuracy highlights the need for targeted OD training and performance monitoring when implementing OD in population-based screening programs.

References

Houwen BBSL, Hassan C, Coupé VMH, et al. Definition of competence standards for optical diagnosis of diminutive colorectal polyps: European Society of Gastrointestinal Endoscopy (ESGE) Position Statement. Endoscopy. 2022;54(1):88-99. doi:10.1055/a-1689-5130

Introduction

Hepatocellular carcinoma (HCC) is the sixth most common malignancy and the third leading cause of cancer-related deaths globally, with increasing incidence and mortality rates. Most patients are diagnosed at advanced stages, missing the opportunity for radical treatment. Sorafenib, a tyrosine kinase inhibitor, is the first-line treatment for advanced HCC; however, drug resistance typically develops within 6 months. Therefore, elucidating the mechanisms of sorafenib resistance and identifying new therapeutic targets are of significant importance. Our study focuses on the role and mechanism of Ribonucleotide Reductase M2 (RRM2) in sorafenib resistance in HCC.

Aims & Methods

The primary objective of this study is to investigate the role of RRM2 in sorafenib resistance in HCC and explore its underlying mechanisms. We aim to clarify whether RRM2 regulates aerobic glycolysis via the HIF-1α/HK2 pathway, thereby affecting sorafenib sensitivity. Our methods include:

• Analyzing RRM2 expression in HCC tissues and its correlation with clinical outcomes, such as disease-free survival (DFS) and overall survival (OS).
• Establishing sorafenib-resistant HCC cell lines (LM3-SR and SMMC7721-SR) and manipulating RRM2 expression using lentiviral vectors for knockdown and overexpression.
• Conducting in vitro experiments to assess the effects of RRM2 on cell proliferation, apoptosis, glycolysis, and sorafenib sensitivity using assays such as CCK8, flow cytometry, and Seahorse analysis.
• Performing in vivo studies using a nude mouse xenograft model to evaluate the impact of RRM2 knockdown on tumor growth and sorafenib efficacy.
• Utilizing RNA-seq, Western blot, PCR, and other techniques to investigate the molecular mechanisms, including the potential regulation of HIF-1α and HK2 by RRM2.

Results

• Clinical Correlation: RRM2 expression was significantly higher in HCC tissues compared to adjacent normal tissues. Higher RRM2 levels were associated with shorter DFS and OS in HCC patients.
• In Vitro Findings: RRM2 knockdown in sorafenib-resistant HCC cells (LM3-SR and SMMC7721-SR) increased sensitivity to sorafenib, as evidenced by reduced cell viability and increased apoptosis. Additionally, RRM2 knockdown decreased glycolysis, as indicated by reduced lactate production and glucose uptake. Conversely, RRM2 overexpression in HCC cells promoted resistance to sorafenib and enhanced glycolysis.
• Molecular Mechanisms: RRM2 regulated the expression of glycolytic enzymes, particularly HK2, through the HIF-1α pathway. Knockdown of RRM2 reduced HIF-1α and HK2 expression, while overexpression of HIF-1α or HK2 could reverse the effects of RRM2 knockdown on glycolysis and sorafenib sensitivity.
• In Vivo Validation: In a nude mouse xenograft model, RRM2 knockdown enhanced the inhibitory effects of sorafenib on tumor growth, as demonstrated by reduced tumor volume and increased apoptosis.

Conclusion

Our study demonstrates that RRM2 plays a crucial role in sorafenib resistance in HCC by regulating aerobic glycolysis via the HIF-1α/HK2 pathway. Targeting RRM2 or its downstream pathways may represent a promising strategy to overcome sorafenib resistance and improve therapeutic outcomes in HCC patients. Future work will focus on further elucidating the molecular mechanisms and exploring the potential clinical applications of RRM2 as a therapeutic target.

Disclosure

The authors declare that they have no conflict of interest.

Introduction

Advances in transanal resection techniques have led to the increased use of surgical and endoscopic local excision (LE) as a diagnostic and potentially organ-sparing approach for early-stage (cT1-2N0) rectal cancer (RC). Current international guidelines recommend completion total mesorectal excision (TME) following LE for surgically fit patients with pT2 RC due to the 20-30% overall risk of lymph node metastasis (LNM). However, the risk of LNM is known to vary according to the presence of histological risk factors. Therefore, omitting completion TME in selected patients with pT2 RC may constitute an oncologically safe alternative, provided there are no additional high-risk histological features other than muscularis propria invasion. The aim of this study was to determine the rate of LNM in patients with pT2 RC without additional histological risk factors.

Aims & Methods

Data from two large Dutch multicentre registries were analysed to evaluate the rate of LNM in patients with pT2 RC who underwent surgery between 2012 and 2020. In accordance with the clinical selection criteria for LE, only patients without suspected LNM on baseline imaging (cN0) were included in the study. Patients who received (neo)adjuvant (chemo)radiotherapy were excluded. Treatment strategies included primary TME, surgical LE followed by completion TME, or surgical LE followed by active surveillance with MRI for at least 24 months. Histological risk factors available in both registries were lymphovascular invasion (LVI) and poor tumour differentiation (PD). Definitive LNM status was determined by histology after TME. Patients on active surveillance after LE were classified as LNM-negative if there was no evidence of LNM (cN0) on MRI during a minimum surveillance period of 24 months. The primary study outcome was the rate of LNM in pT2 RC patients without LVI and PD. Secondary outcomes included the association between the two histological risk factors and the rate of LNM using univariable and multivariable analyses adjusted for age and sex.

Results

A total of 334 patients with pT2 RC met the inclusion criteria (mean age 69 years, 64% male). The majority of patients (262/334, 78%) underwent primary TME, while initial surgical LE was performed in 72/334 (22%). Within the LE group, subsequent TME surgery was performed in 59/72 (82%) patients, either as completion surgery (n=51) or as salvage surgery during the follow-up period (n=8). The remaining 13/72 (18%) patients underwent active surveillance for at least 24 months without suspicion of LNM on MRI during a median follow-up of 42 months (IQR 32-55). The overall rate of LNM in the cohort was 17% (55/334). In the 266/334 (80%) patients without LVI and PD, the rate of LNM was 13% (34/266). The presence of either LVI alone or PD alone resulted in LNM rates of 31% (18/58) and 14% (1/7), respectively. When both LVI and PD were present, LNM occurred in 2 out of 3 cases. In our study, only LVI was identified as an independent predictor of LNM in multivariable analysis (p<0.001; OR = 3.1, 95% CI 1.6-5.9).

Conclusion

In this large retrospective surgical cohort of patients with pT2 RC, the absence of LVI and PD was associated with a 13% risk of LNM. However, more detailed histological reassessment including risk factors such as tumour budding and perineural invasion may identify a subgroup of pT2 RC with an even lower risk of LNM. This may allow the omission of completion TME.

Introduction

YTH N⁶-methyladenosine RNA binding protein 1 (YTHDF1) is a N⁶-methyladenosine (m⁶A) reader that is overexpressed in colorectal cancer (CRC), and it induces colorectal tumorigenesis and metastatic progression. Nevertheless, no pharmacological approach is available for targeting YTHDF1.

Aims & Methods

To this end, we performed Epi-Drug CRISPR/Cas9 library screening for druggable targets that impair the oncogenic function of YTHDF1 in CRC.
Epi-Drug CRISPR/Cas9 library screen was used to identify genes selectively depleted in CRC cells overexpressing YTHDF1. Clinical significance of gene candidates was evaluated in independent CRC patient cohorts. Interplay between gene candidates and YTHDF1 using integrative m⁶A sequencing, RNA sequencing, Ribosome-sequencing, ribosome profiling analyses, and liquid chromatography-mass spectrometry. Targeting YTHDF1 druggable targets were assessed by pharmacological inhibitors and vesicle-like nanoparticles (VNPs)-encapsulated siRNA.

Results

Using Epi-Drug CRISPR/Cas9 library screen, we identified RUVBL1 and RUVBL2 as top essential druggable target genes in CRC cells overexpressing YTHDF1. RUVBL1/2 are overexpressed in primary CRCs from two independent cohorts (Beijing and TCGA) and they predict poor survival in patients with CRC. Functionally, silencing RUVBL1 or RUVBL2 suppressed tumorigenesis of YTHDF1-overexpressing cell lines, primary CRC organoids and CRC xenografts in nude mice. Mechanistically, YTHDF1 directly binds to m⁶A-modified RUVBL1/2, as determined by integrated m6A sequencing, RNA sequencing, ribosome sequencing, leading to increased RUVBL1/2protein translation. Interestingly, co-immunoprecipitation and mass spectrometry revealed that RUVBL1/2 proteins directly interact with YTHDF1 and its associated translation initiation factors. Moreover, RUVBL1/2 functions as the essential components of YTHDF1 translational complex, and their depletion abrogated YTHDF1-induced protein translation and bio-synthesis. As a consequence, RUVBL1/2 knockout largely abolished YTHDF1-induced oncogenic signaling, especially the activation of MAPK and PI3K signaling pathways. To verify RUVBL1/2 as potential therapeutic targets in YTHDF1-expressing CRC, we next employed pharmacological RUVBL1/2 inhibitors and nanoparticle-encapsulated siRUVBL1/2 to target RUVBL1/2 in CRC models. In support of our notion, targeting RUVBL1/2 with pharmacological inhibitors or in vivo siRNA delivery suppressed the growth of YTDHF1-overexpressing CRC cell in vitro and regressed tumor xenografts in vivo.

Conclusion

Our study identified RUVBL1/2 as druggable target genes of YTHDF1. Targeting RUVBL1/2 is a promising strategy for treatment of CRC with high YTHDF1 expression.