The post-chemotherapy changes of tumor physical microenvironment: Targeting extracellular matrix to address chemoresistance

New insights into cancer pathology learned from the dynamics of cancer-associated fibroblasts

Paget's "Seed and Soil" theory, proposed in 1889, emphasizes the importance of the microenvironment where cancer cells grow in metastatic sites. Over a century later, this concept remains a cornerstone in comprehending cancer biology and devising treatment strategies. The "Seed and Soil" theory, which initially explained how cancer spreads to distant organs, now also applies to the tumor microenvironment (TME) within primary tumors. This theory emphasizes the critical interaction between cancer cells ("seeds") and their surrounding environment ("soil") and how this interaction affects both tumor progression within the primary site and at metastatic sites. An important point to note is that the characteristics of the TME are not static but dynamic, undergoing substantial changes during tumor progression and after treatment with therapeutic drugs. Cancer-associated fibroblasts (CAFs), recognized as the principal noncancerous cellular component within the TME, play multifaceted roles in tumor progression including promoting angiogenesis, remodeling the extracellular matrix, and regulating immune responses. In this comprehensive review, we focus on the findings regarding how the dynamics of CAFs contribute to cancer progression and drug sensitivity. Understanding the dynamics of CAFs could provide new insights into cancer pathology and lead to important advancements in cancer research and treatment.

Gut mechanoimmunology: Shaping immune response through physical cues

The gut immune system embodies a complex interplay between the gut mucosal barrier, the host's immune cells, and gut microbiota. These components exist within a dynamic environment characterized by a variety of physical cues, e.g., compression, tension, shear stress, stiffness, and viscoelasticity. The physical cues can be modified under specific pathological conditions. Given their dynamic nature, comprehending the specific effects of these physical cues on the gut immune system is critical for pathological and therapeutic studies of intestinal immune-related diseases. This review aims to discuss how physical cues influence gut immunology by affecting the gut mucosal barrier, host immune cells, and gut microbiota, defining this concept as gut mechanoimmunology. This review seeks to highlight that an enhanced understanding of gut mechanoimmunology carries therapeutic implications, not only for intestinal diseases but also for extraintestinal diseases.

[Hepatocellular Carcinoma-Derived Exosomes: Key Players in Intercellular Communication Within the Tumor Microenvironment]

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths in the world. Due to the insidious onset and rapid progression and a lack of effective treatments, the prognosis of patients with HCC is extremely poor, with the average 5-year survival rate being less than 10%. The tumor microenvironment (TME), the internal environment in which HCC develops, can regulate the oncogenesis, development, invasion, and metastasis of HCC. During the process of cancer progression, HCC cells can regulate the biological behaviors of tumor cells, cancer-associated fibroblasts, cancer-associated immune cells, and other cells in the TME by releasing exosomes containing specific signals, thereby promoting cancer progression. However, the exact molecular mechanisms and the roles of exosomes in the specific cellular regulation of these processes are not fully understood. Herein, we summarized the TME components of HCC, the sources and the biological traits of exosomes in the TME, and the impact of mechanical factors on exosomes. In addition, special attention was given to the discussion of the effects of HCC-exosomes on different types of cells in the microenvironment. There are still many difficulties to be overcome before exosomes can be applied as carriers in clinical cancer treatment. First of all, the homogeneity of exosomes is difficult to ensure. Secondly, exosomes are mainly administered through subcutaneous injection. Although this method is simple and easy to implement, the absorption efficiency is not ideal. Thirdly, exosome extraction methods are limited in number and inefficient, making it difficult to prepare exosomes in large quantities. It is important to ensure that exosomes are used in sufficient quantities to trigger an effective tumor immune response, especially for exosome-mediated tumor immunotherapy. With the improvement in identification, isolation, and purification technology, exosomes are expected to be successfully used in the clinical diagnosis of early-stage HCC and the clinical treatment of liver cancer.