Immune-Modulating Effects of Conventional Therapies in Colorectal Cancer

Colorectal Cancer Immunotherapy: State of the Art and Future Directions

Cancer immunotherapy has become an indispensable mode of treatment for a multitude of solid tumor cancers. Colorectal cancer (CRC) has been one of the many cancer types to benefit from immunotherapy, especially in advanced disease where standard treatment fails to prevent recurrence or results in poor survival. The efficacy of immunotherapy in CRC has not been without challenge, as early clinical trials observed dismal responses in unselected CRC patients treated with checkpoint inhibitors. Many studies and clinical trials have since refined immunotherapies available for CRC, solidifying immunotherapy as a powerful asset for CRC treatment. This review article examines CRC immunotherapies, from their foundation, through emerging avenues for improvement, to future directions.

Exosomes-delivered PD-L1 siRNA and CTLA-4 siRNA protect against growth and tumor immune escape in colorectal cancer

OBJECTIVE

This study aims to dissect impacts of exosomes-delivered PD-L1 and CTLA-4 siRNAs on colorectal cancer (CRC) progression and immune responses.

METHODS

Exosomes containing PD-L1 siRNA and CTLA-4 siRNA were prepared and utilized to treat CRC cells to evaluate their effects. A tumor-bearing mouse model was established for verification.

RESULTS

Exosomes containing PD-L1 siRNA and CTLA-4 siRNA repressed malignant features of CRC cells and restrained tumor growth and activated tumor immune responses in vivo. Co-culture of CRC cells treated with exosomes containing PD-L1 siRNA and CTLA-4 siRNA with human CD8+ T cells increased the percentage of CD8+ T cells, decreased the apoptotic rate of CD8+ T cells, elevated IL-2, IFN-γ, and TNF-α expression in cell supernatants, reduced adherent density of CRC cells, augmented the positive rate of CRC cells, and subdued tumor immune escape.

CONCLUSION

Exosomes containing PD-L1 siRNA and CTLA-4 siRNA suppressed CRC progression and enhanced tumor immune responses.

Combining radiation and the ATR inhibitor berzosertib activates STING signaling and enhances immunotherapy via inhibiting SHP1 function in colorectal cancer

BACKGROUND

Immune checkpoint inhibitors (ICIs) targeting programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) have shown a moderate response in colorectal cancer (CRC) with deficient mismatch repair (dMMR) functions and poor response in patients with proficient MMR (pMMR). pMMR tumors are generally immunogenically "cold", emphasizing combination strategies to turn the "cold" tumor "hot" to enhance the efficacy of ICIs. ATR inhibitors (ATRi) have been proven to cooperate with radiation to promote antitumor immunity, but it is unclear whether ATRi could facilitate the efficacy of IR and ICI combinations in CRCs. This study aimed to investigate the efficacy of combining ATRi, irradiation (IR), and anti-PD-L1 antibodies in CRC mouse models with different microsatellite statuses.

METHODS

The efficacy of combining ATRi, IR, and anti-PD-L1 antibodies was evaluated in CRC tumors. The tumor microenvironment and transcriptome signatures were investigated under different treatment regimens. The mechanisms were explored via cell viability assay, flow cytometry, immunofluorescence, immunoblotting, co-immunoprecipitation, and real-time quantitative PCR in multiple murine and human CRC cell lines.

RESULTS

Combining ATRi berzosertib and IR enhanced CD8⁺ T cell infiltration and enhanced the efficacy of anti-PD-L1 therapy in mouse CRC models with different microsatellite statuses. The mechanistic study demonstrated that IR + ATRi could activate both the canonical cGAS-STING-pTBK1/pIRF3 axis by increasing cytosolic double-stranded DNA levels and the non-canonical STING signaling by attenuating SHP1-mediated inhibition of the TRAF6-STING-p65 axis, via promoting SUMOylation of SHP1 at lysine 127. By boosting the STING signaling, IR + ATRi induced type I interferon-related gene expression and strong innate immune activation and reinvigorated the cold tumor microenvironment, thus facilitating immunotherapy.

CONCLUSIONS

The combination of ATRi and IR could facilitate anti-PD-L1 therapy by promoting STING signaling in CRC models with different microsatellite statuses. The new combination strategy raised by our study is worth investigating in the management of CRC.

Intracellular and extracellular factors of colorectal cancer liver metastasis: a pivotal perplex to be fully elucidated

Metastasis is the leading cause of death in colorectal cancer (CRC) patients, and the liver is the most common site of metastasis. Tumor cell metastasis can be thought of as an invasion-metastasis cascade and metastatic organotropism is thought to be a process that relies on the intrinsic properties of tumor cells and their interactions with molecules and cells in the microenvironment. Many studies have provided new insights into the molecular mechanism and contributing factors involved in CRC liver metastasis for a better understanding of the organ-specific metastasis process. The purpose of this review is to summarize the theories that explain CRC liver metastasis at multiple molecular dimensions (including genetic and non-genetic factors), as well as the main factors that cause CRC liver metastasis. Many findings suggest that metastasis may occur earlier than expected and with specific organ-anchoring property. The emergence of potential metastatic clones, the timing of dissemination, and the distinct routes of metastasis have been explained by genomic studies. The main force of CRC liver metastasis is also thought to be epigenetic alterations and dynamic phenotypic traits. Furthermore, we review key extrinsic factors that influence CRC cell metastasis and liver tropisms, such as pre-niches, tumor stromal cells, adhesion molecules, and immune/inflammatory responses in the tumor microenvironment. In addition, biomarkers associated with early diagnosis, prognosis, and recurrence of liver metastasis from CRC are summarized to enlighten potential clinical practice, including some markers that can be used as therapeutic targets to provide new perspectives for the treatment strategies of CRC liver metastasis.

Metastatic Colorectal Cancer

International experts in the study of metastatic colorectal cancer (mCRC) present this series of 14 articles (eleven original articles and three literature reviews) [...].