PDP1 promotes KRAS mutant colorectal cancer progression by serving as a scaffold for BRAF and MEK1.

The oncogenic role of KRAS in colorectal cancer (CRC) progression is well-established. Despite this, identifying effective therapeutic targets for KRAS-mutated CRC remains a significant challenge. This study identifies pyruvate dehydrogenase phosphatase catalytic subunit 1 (PDP1) as a previously unrecognized yet crucial regulator in the progression of KRAS mutant CRC. A substantial upregulation of PDP1 expression is observed in KRAS mutant CRC cells and tissues compared to wild-type KRAS samples, which correlates with poorer prognosis. Functional experiments elucidate that PDP1 accelerates the malignance of KRAS mutant CRC cells, both in vitro and in vivo. Mechanistically, PDP1 acts as a scaffold, enhancing BRAF and MEK1 interaction and activating the MAPK signaling, thereby promoting CRC progression. Additionally, transcription factor KLF5 is identified as the key regulator for PDP1 upregulation in KRAS mutant CRC. Crucially, targeting PDP1 combined with MAPK inhibitors exhibits an obvious inhibitory effect on KRAS mutant CRC. Overall, PDP1 is underscored as a vital oncogenic driver and promising therapeutic target for KRAS mutant CRC.

Biomarkers of Pathologic Complete Response to Neoadjuvant Immunotherapy in Mismatch Repair-Deficient Colorectal Cancer.

PURPOSE: Immune checkpoint inhibitors (ICI) have become the standard of care for patients with mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) colorectal cancer. However, biomarkers of response to ICI are still lacking. EXPERIMENTAL DESIGN: Forty-two patients with dMMR colorectal cancer treated with neoadjuvant PD-1 blockade were prospectively enrolled. To identify biomarkers of pathologic complete response (pCR) to neoadjuvant therapy, we analyzed genomic and transcriptomic profiles based on next-generation sequencing, and immune cell density based on multiplex immunofluorescence (mIF) staining. An integrated analysis of single-cell RNA sequencing from our previous study and GSE178341, as well as mIF was performed to further explore the significance of the tumor microenvironment (TME) on pCR response. RESULTS: The tumor mutation burden of both tumor tissue and plasma blood samples was comparable between the pCR and non-pCR groups, while HLA-DQA1 and HLA-DQB1 were significantly overexpressed in the pCR group. Gene signature enrichment analysis showed that pathways including T-cell receptor pathway, antigen presentation pathway were significantly enriched in the pCR group. In addition, higher pre-existing CD8+ T-cell density was associated with pCR response (767.47 per.mm2 vs. 326.64 per.mm2, P = 0.013 Wilcoxon test). Further integrated analysis showed that CD8+ T cells with low PD-1 expression (PD-1lo CD8+ T cells) expressing high levels of TRGC2, CD160, and KLRB1 and low levels of proliferated and exhausted genes were significantly associated with pCR response. CONCLUSIONS: Immune-associated transcriptomic features, particularly CD8+ T cells were associated with pCR response to ICI in dMMR colorectal cancer. Heterogeneity of TME within dMMR colorectal cancer may help to discriminate patients with complete response to neoadjuvant ICI.

Dynamic heterogeneity of colorectal cancer during progression revealed clinical risk-associated cell types and regulations in single-cell resolution and spatial context.

Background: Tumor heterogeneity is contributed by tumor cells and the microenvironment. Dynamics of tumor heterogeneity during colorectal cancer (CRC) progression have not been elucidated. Methods: Eight single-cell RNA sequencing (scRNA-seq) data sets of CRC were included. Milo was utilized to reveal the differential abundance of cell clusters during progression. The differentiation trajectory was imputed by using the Palantir algorithm and metabolic states were assessed by using scMetabolism. Three spatial transcription sequencing (ST-seq) data sets of CRC were used to validate cell-type abundances and colocalization. Cancer-associated regulatory hubs were defined as communication networks affecting tumor biological behaviors. Finally, quantitative reverse transcription polymerase chain reaction and immunohistochemistry staining were performed for validation. Results: TM4SF1+, SOX4+, and MKI67+ tumor cells; CXCL12+ cancer-associated fibroblasts; CD4+ resident memory T cells; Treg; IgA+ plasma cells; and several myeloid subsets were enriched in stage IV CRC, most of which were associated with overall survival of patients. Trajectory analysis indicated that tumor cells from patients with advanced-stage CRC were less differentiated, when metabolic heterogeneity showed a highest metabolic signature in terminal states of stromal cells, T cells, and myeloid cells. Moreover, ST-seq validated cell-type abundance in a spatial context and also revealed the correlation of immune infiltration between tertiary lymphoid structures and tumors followed by validation in our cohort. Importantly, analysis of cancer-associated regulatory hubs revealed a cascade of activated pathways including leukocyte apoptotic process, MAPK pathway, myeloid leukocyte differentiation, and angiogenesis during CRC progression. Conclusions: Tumor heterogeneity was dynamic during progression, with the enrichment of immunosuppressive Treg, myeloid cells, and fibrotic cells. The differential state of tumor cells was associated with cancer staging. Assessment of cancer-associated regulatory hubs suggested impaired antitumor immunity and increased metastatic ability during CRC progression.

Tumor-secreted IFI35 promotes proliferation and cytotoxic activity of CD8+ T cells through PI3K/AKT/mTOR signaling pathway in colorectal cancer.

BACKGROUND: A large proportion of the patients with cancer do not respond to immunotherapies. Recent studies suggested an important role for tumor-infiltrating cytotoxic T lymphocytes (CTL) in enhancing response to immunotherapy. Here, we aim to identify gene that induce proliferative and cytotoxic states of CD8+ T cells, and to investigate its effect on CAR-T cells against colorectal cancer. METHODS: Correlation between the expression of IFI35 with the activation and cytotoxicity of CD8+ T cells was assessed with TCGA and proteomic databases. Then we constructed murine colon cancer cells over-expressing IFI35 and tested their effect on anti-tumor immunity in both immunodeficient and immunocompetent mouse models. Flow cytometry and immunohistochemistry were performed to assess the immune microenvironment. Western blot analysis was used to identify the potential down-stream signaling pathway regulated by IFI35. We further investigated the efficacy of the rhIFI35 protein in combination with immunotherapeutic treatment. RESULTS: The transcriptional and proteomic analysis of the activation and cytotoxicity of CD8+ T cells in human cancer samples demonstrated that IFI35 expression is correlated with increased CD8+ T cell infiltration and predicted a better outcome in colorectal cancer. The number and cytotoxicity of CD8+ T cells were significantly increased in IFI35-overexpressing tumors. Mechanistically, we identified that the IFNγ-STAT1-IRF7 axis stimulated IFI35 expression, and that IFI35-mediated regulation of CD8+ T cell proliferation and cytotoxicity was dependent on PI3K/AKT/mTOR signaling pathway in vitro. Furthermore, IFI35 protein enhanced the efficacy of CAR-T cells against colorectal cancer cells. CONCLUSION: Our findings identify IFI35 as a new biomarker that can enhance the proliferation and function of CD8+ T cells, as well as increase the efficacy of CAR-T cells against colorectal cancer cells.

MAP7D2 reduces CD8+ cytotoxic T lymphocyte infiltration through MYH9-HMGB1 axis in colorectal cancer.

Immune checkpoint inhibitors (ICIs) represent a new paradigm in cancer immunotherapy, but can be largely restricted by the limited presence of CD8+ cytotoxic T lymphocytes (CTLs) in colorectal cancer (CRC) patients with microsatellite stable (MSS) tumors. Here, through next-generation sequencing, we identify microtubule-associated protein 7 domain 2 (MAP7D2) as an exploitable therapeutic maneuver to improve the efficacy of ICIs for MSS CRC therapy. In human CRC tissues, MAP7D2 expression is significantly increased in MSS CRC, and MAP7D2 adversely correlates with the presence of antitumor T lymphocytes. In vitro and in vivo experiments demonstrate that MAP7D2 knockdown significantly increases the infiltration of CD8+ CTLs, thereby inhibiting tumor progression and improving the efficacy of ICIs in MSS CRC murine models. Mechanistically, MAP7D2 interacts with MYH9 and protects it from ubiquitin-mediated degradation, subsequently decreasing the secretion of HMGB1, which suppresses the infiltration of CD8+ CTLs in MSS CRC. These findings highlight the importance of MAP7D2 in determining the infiltration of CD8+ CTLs and indicate that targeting MAP7D2 in MSS CRC may present a novel antitumor immunotherapy.

LncRNA DANCR represses Doxorubicin-induced apoptosis through stabilizing MALAT1 expression in colorectal cancer cells.

Long non-coding RNA (lncRNA) DANCR has been reported to participate in key processes such as stem cell differentiation and tumorigenesis. In a high throughput screening for lncRNAs involved in Doxorubicin-induced apoptosis, we found DANCR was suppressed by Doxorubicin and it acted as an important repressor of apoptosis in colorectal cancer. Further studies demonstrated that DANCR promoted the oncogenic lncRNA MALAT1 expression via enhancing the RNA stability of MALAT1 to suppress apoptosis. MALAT1 could efficiently mediate the suppressive function of DANCR on apoptosis. Mechanistic studies found the RNA-binding protein QK served as an interacting partner of both DANCR and MALAT1, and the protein level of QK was subjected to the regulation by DANCR. Furthermore, QK was able to modulate the RNA stability of MALAT1, and the interaction between QK and MALAT1 was controlled by DANCR. In addition, QK could mediate the function of DANCR in regulating the expression of MALAT1 and suppressing apoptosis. These results revealed DANCR played a critical role in Doxorubicin-induced apoptosis in colorectal cancer cells, which was achieved by the interaction between DANCR and QK to enhance the expression of MALAT1.

Continent Ileostomy as an Alternative to End Ileostomy.

Continent ileostomy (CI) was once a prevalent surgical technique for patients who required total proctocolectomy but then gave way to ileal pouch-anal anastomosis (IPAA) after 1980. Although IPAA has been the gold standard procedure preferred by most patients when total proctocolectomy is required, due to its imitation of physiological function of rectum and preserved function of anus, various complications have been observed with a relatively high rate of morbidity that could affect pouch longevity. Once serious complications such as pelvic abscesses and/or fistula occur, the pouch often needs to be removed. In addition, for some patients with a shortened small intestine or foreshortened mesentery, it is impossible for the ileal pouch to reach the pelvic floor, thus making the creation of an IPAA difficult. Previously, most of these patients would be referred for an end ileostomy, with an associated poor quality of life. In this circumstance, we propose that CI may deserve a reappraisal and serve as an alternative. In this article, we review the indications, contraindications, technique evolution, and outcomes of CI.