“Cold” colorectal cancer faces a bottleneck in immunotherapy

Humanized mouse models of KRAS-mutated colorectal and pancreatic cancers with HLA-class-I match for pre-clinical evaluation of cancer immunotherapies

Cancer immunotherapy promises to treat challenging cancers including KRAS-mutated colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC). However, pre-clinical animal models that better mimic patient tumor and immune system interactions are required. While humanized mice are promising vehicles for pre-clinical immunotherapy testing, currently used cancer models retain limitations, such as lack of a human thymus for human leukocyte antigen (HLA)-based education of human T cells. As cytotoxic T lymphocyte (CTL) activity underlies many immunotherapies, we developed more clinically relevant KRAS-mutated CRC and PDAC humanized cancer models using transgenic NRG-A2 mice expressing HLA-A2.1 to enable HLA-class-I match between mouse tissues (including the thymus), the humanized immune system and human tumors. Using these novel humanized cancer models and a CTL-mediated combination (immuno)therapy with clinical potential, we were able to recapitulate the complexity and therapy-induced changes reported in patient biopsies, demonstrating the use of these HLA-matched models for pre-clinical validation of novel immunotherapies.

Curcumin exerts anti-tumor activity in colorectal cancer via gut microbiota-mediated CD8+ T Cell tumor infiltration and ferroptosis

Colorectal cancer (CRC), as a high-incidence malignancy, continues to present significant challenges in prevention, screening, and treatment. Curcumin (Cur) exhibits notable anti-inflammatory and anticancer properties. Despite its poor solubility in water and low bioavailability, high concentrations of Cur are detected in the gastrointestinal tract after oral administration, suggesting that it may directly interact with the gut microbiota and exert regulatory effects. This study aims to explore the mechanisms by which Cur improves CRC by modulating gut microbiota. Firstly, we evaluated the effect of Cur on CRC cell viability in vitro using the MTT assay, and the results showed a significant inhibitory effect on CRC cell growth. The IC50 values for Cur in CT26 and RKO cells were 23.52 μM, 16.11 μM, and 13.62 μM at 24, 48, and 72 hours, respectively, and 26.3 μM, 16.52 μM, and 14.22 μM at 24, 48, and 72 hours, respectively. Cur induced apoptosis and caused G2 phase cell cycle arrest in tumor cells. Subsequently, we established a CRC mouse model. Oral administration of Cur at 15 mg kg-1 and 30 mg kg-1 inhibited CRC progression, as evidenced by reduced tumor volume, histological analysis, immunohistochemistry, and an increased number of CD8+ T cells infiltrating the tumors. Ferroptosis in tumor cells was also observed. Cur partially restored the gut microbiota of CRC mice, altering the abundance and diversity of the gut microbiota and affecting serum metabolite distribution, with significant increases in the abundance of SCFA-producing microbes such as Lactobacillus and Kineothrix. To verify causality, we designed a fecal microbiota transplantation (FMT) experiment. Compared with CRC mice, the fecal microbiota from Cur-treated mice significantly alleviated CRC symptoms, including slowed tumor growth, enhanced CD8+ T cell tumor infiltration, and induced ferroptosis in tumor cells. Additionally, when gut microbiota was depleted with antibiotics, Cur's antitumor effects disappeared, suggesting that Cur mitigates CRC in a gut microbiota-dependent manner. These findings provide new insights into the mechanisms underlying CRC and propose novel therapeutic interventions, emphasizing the interaction between gut microbiota and immune responses within the tumor immune microenvironment (TIME).

Inhibition of insulin-like growth factors increases production of CXCL9/10 by macrophages and fibroblasts and facilitates CD8+ cytotoxic T cell recruitment to pancreatic tumours

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy with an urgent unmet clinical need for new therapies. Using a combination of in vitro assays and in vivo preclinical models we demonstrate that therapeutic inhibition of the IGF signalling axis promotes the accumulation of CD8+ cytotoxic T cells within the tumour microenvironment of PDAC tumours. Mechanistically, we show that IGF blockade promotes macrophage and fibroblast production of the chemokines CXCL9 and CXCL10 to facilitate CD8+ T cell recruitment and trafficking towards the PDAC tumour. Exploring this pathway further, we show that IGF inhibition leads to increased STAT1 transcriptional activity, correlating with a downregulation of the AKT/STAT3 signalling axis, in turn promoting Cxcl9 and Cxcl10 gene transcription. Using patient derived tumour explants, we also demonstrate that our findings translate into the human setting. PDAC tumours are frequently described as "immunologically cold", therefore bolstering CD8+ T cell recruitment to PDAC tumours through IGF inhibition may serve to improve the efficacy of immune checkpoint inhibitors which rely on the presence of CD8+ T cells in tumours.

The Interplay among Wnt/β-catenin Family Members in Colorectal Adenomas and Surrounding Tissues

BACKGROUND

The colorectal adenoma undergoes neoplastic progression via the normal epithelium-adenoma-adenocarcinoma sequence as reported in the Vogelgram. The hazard of developing a tumor is deeply associated with the number and size of adenomas and their subtype. Adenomatous polyps are histologically categorized as follows: approximately 80-90% are tubular, 5-15% are villous, and 5-10% are tubular/villous. Given the higher risk of a malignant transformation observed in tubular/villous adenomas, patients diagnosed with adenomatous polyposis are at an improved risk of developing CRC. The Wnt/β-catenin pathway plays a key role in the onset of colorectal adenoma; in particular, intestinal cells first acquire loss-of-function mutations in the APC gene that induce the formation of adenomas.

METHODS

Wnt/β-catenin pathway APC, Wnt3a, Wnt5a, LEF1, and BCL9 genes and protein expression analyses were conducted by qRT-PCR and western blot in 68 colonic samples (polyps and adjacent mucosa) from 41 patients, of which 17 were affected by FAP. Ten normal colonic mucosal samples were collected from 10 healthy donors.

RESULTS

In this study, both the APC gene and protein were less expressed in the colon tumor compared to the adjacent colonic mucosa. Conversely, the activated β-catenin was more expressed in polyps than in the adjacent mucosa. All results confirmed the literature data on carcinomas. A statistically significant correlation between Wnt3a and BCL9 both in polyps and in the adjacent mucosa underlines that the canonical Wnt pathway is activated in early colon carcinogenesis and that the adjacent mucosa is already altered.

CONCLUSION

This is the first study analyzing the difference in expression of the Wnt/β-catenin pathway in human colorectal adenomas. Understanding the progression from adenomas to colorectal carcinomas is essential for the development of new therapeutic strategies and improving clinical outcomes with the use of APC and β-catenin as biomarkers.

Immune landscape and response to oncolytic virus-based immunotherapy

Oncolytic virus (OV)-based immunotherapy has emerged as a promising strategy for cancer treatment, offering a unique potential to selectively target malignant cells while sparing normal tissues. However, the immunosuppressive nature of tumor microenvironment (TME) poses a substantial hurdle to the development of OVs as effective immunotherapeutic agents, as it restricts the activation and recruitment of immune cells. This review elucidates the potential of OV-based immunotherapy in modulating the immune landscape within the TME to overcome immune resistance and enhance antitumor immune responses. We examine the role of OVs in targeting specific immune cell populations, including dendritic cells, T cells, natural killer cells, and macrophages, and their ability to alter the TME by inhibiting angiogenesis and reducing tumor fibrosis. Additionally, we explore strategies to optimize OV-based drug delivery and improve the efficiency of OV-mediated immunotherapy. In conclusion, this review offers a concise and comprehensive synopsis of the current status and future prospects of OV-based immunotherapy, underscoring its remarkable potential as an effective immunotherapeutic agent for cancer treatment.

Prognostic Implications of Intratumoral Budding in Colorectal Cancer: Detailed Analysis Based on Tumor-Infiltrating Lymphocytes

BACKGROUND

This study aims to understand the clinical and pathological importance of intratumoral budding (ITB) in colorectal cancer (CRC) and its relationship with tumor-infiltrating lymphocytes (TILs). CRCs can be classified into hot (high immunoscore (IS)) and cold (low IS) tumors.

METHODS

We investigated the number of ITBs in a hotspot area and categorized them into high-ITB (≥5) and low-ITB (<5) groups. The clinicopathological significance of ITB in human CRCs was evaluated, and a detailed analysis based on tumor-infiltrating lymphocytes (TILs) was also performed.

RESULTS

High ITB was identified in 59 of 266 CRC cases (22.2%). High ITB significantly correlated with a poorly differentiated tumor, lympho-vascular invasion, perineural invasion, higher pT stage, lymph node metastasis, and higher metastatic lymph node ratio. High ITB was also significantly correlated with a low IS and low CD8-positive lymphocytic infiltrate. The number of ITBs was substantially higher in the low-IS group than in the high-IS group (3.28 ± 3.31 vs. 2.19 ± 2.59; p = 0.005). High ITB significantly correlated with worse overall survival (p = 0.004). In the low-IS group, CRCs with high ITB had a significantly worse prognosis than those with low ITB (p = 0.021). However, there was no significant difference in prognosis between the high- and low-ITB groups in the high-IS group (p = 0.498).

CONCLUSIONS

Taken together, high ITB was significantly correlated with aggressive tumor behaviors and worse survival in patients with CRCs. In addition, ITB can be useful for the prognostic stratification of CRCs with low IS.