Abstract
Gap junction proteins are expressed in cancer stem cells and non-stem cancer cells of many tumors. As the morphology and assembly of gap junction channels are crucial for their function in intercellular communication, one focus of our review is to outline the data on gap junction plaque morphology available for cancer cells. Electron microscopic studies and freeze-fracture analyses on gap junction ultrastructure in cancer are summarized. As the presence of gap junctions is relevant in solid tumors, we exemplarily outline their role in glioblastomas and in breast cancer. These were also shown to contain cancer stem cells, which are an essential cause of tumor onset and of tumor transmission into metastases. For these processes, gap junctional communication was shown to be important and thus we summarize, how the expression of gap junction proteins and the resulting communication between cancer stem cells and their surrounding cells contributes to the dissemination of cancer stem cells via blood or lymphatic vessels. Based on their importance for tumors and metastases, future cancer-specific therapies are expected to address gap junction proteins. In turn, gap junctions also seem to contribute to the unattainability of cancer stem cells by certain treatments and might thus contribute to therapeutic resistance.
Highlights
Worldwide, the majority of deaths are caused by non-communicable diseases
Cancer stem cells express connexins. These connexins seem to be responsible for gap junctional intercellular communication (GJIC) and for survival, proliferation and self-renewal of cancer stem cells (CSCs) like they are in other cells [35]
Taken studies of the last 40 years of cancer research together, gap junctions clearly participate in the processes of carcinogenesis and cancer
Summary
With 9.5 million cancer deaths (non-melanoma skin cancer excluded) estimated by the GLOBOCAN for 2018, cancer is the second leading cause of death worldwide [1,2]. For this reason, understanding the mechanisms behind carcinogenesis is of utmost importance in cancer research and for the development of new therapies. Defects in intercellular communication will result in impaired cell homeostasis and is likely to lead to the development of uncontrolled proliferation (growth), namely cancer [12,13]. Several recent review articles discuss those general aspects in detail [33,34,35]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
