Paracrine signaling in stem cell renewal and in neoplastic tumor growth

4-Hydroxynonenal Promotes Colorectal Cancer Progression through Regulating Cancer Stem Cell Fate

AIMS

Tumor microenvironment (TME) plays a crucial role in sustaining cancer stem cells (CSCs). 4-hydroxynonenal (4-HNE) is abundantly present in the TME of colorectal cancer (CRC). However, the contribution of 4-HNE to CSCs and cancer progression remains unclear. This study aimed to investigate the impact of 4-HNE on the regulation of CSC fate and tumor progression.

METHODS

Human CRC cells were exposed to 4-HNE, and CSC signaling was analyzed using quantitative real-time PCR, immunofluorescent staining, fluorescence-activated cell sorting, and bioinformatic analysis. Tumor-promoting role of 4-HNE was confirmed using a xenograft model.

RESULTS

Exposure of CRC cells to 4-HNE activated non-canonical Hedgehog (HH) signaling and homologous recombination repair (HRR) pathways in LGR5+ CSCs. Furthermore, blocking HH signaling led to a significant increase in the expression of γH2AX, indicating that 4-HNE induces double-stranded DNA breaks (DSBs) and simultaneously activates HH signaling to protect CSCs from 4-HNE-induced damage via the HRR pathway. Additionally, 4-HNE treatment increased the population of LGR5+ CSCs and promoted asymmetric division in these cells, leading to enhanced self-renewal and differentiation. Notably, 4-HNE also promoted xenograft tumor growth and activated CSC signaling in vivo.

INNOVATION AND CONCLUSION

These findings demonstrate that 4-HNE, as a signaling inducer in the TME, activates the non-canonical HH pathway to shield CSCs from oxidative damage, enhances the proliferation and asymmetric division of LGR5+ CSCs, and thereby facilitates tumor growth. These novel insights shed light on the regulation of CSC fate within the oxidative TME, offering potential implications for understanding and targeting CSCs for CRC therapy.

Genomic landscape of gastric cancer: molecular classification and potential targets

Gastric cancer imposes a considerable health burden worldwide, and its mortality ranks as the second highest for all types of cancers. The limited knowledge of the molecular mechanisms underlying gastric cancer tumorigenesis hinders the development of therapeutic strategies. However, ongoing collaborative sequencing efforts facilitate molecular classification and unveil the genomic landscape of gastric cancer. Several new drivers and tumorigenic pathways in gastric cancer, including chromatin remodeling genes, RhoA-related pathways, TP53 dysregulation, activation of receptor tyrosine kinases, stem cell pathways and abnormal DNA methylation, have been revealed. These newly identified genomic alterations await translation into clinical diagnosis and targeted therapies. Considering that loss-of-function mutations are intractable, synthetic lethality could be employed when discussing feasible therapeutic strategies. Although many challenges remain to be tackled, we are optimistic regarding improvements in the prognosis and treatment of gastric cancer in the near future.