Cancer stem cells are being investigated as the originating cell for cancer. Cancer stem cells are thought to be an abnormal version of a normal stem cell, which can generate every type of cell found in the cancerous tumor. Science identified viral infections, within cancer stem cells; and theorized the viruses caused a normal stem cell to become a cancer stem cell.
A 2015 laboratory study (posted 6/20/19) showed doxycycline and azithromax eradicated cancer stem cells across multiple tumor types. Viruses are thought not to be treatable with antibiotics. The effectiveness of antibiotics in killing cancer stem cells supports an intracellular bacteria, with the same or similar properties as cancer, infected normal stem cells and caused or contributed to development of cancer stem cells.
Viral infections and intracellular bacterial infections may be causing normal stem cells to become cancer stem cells, alone or in combination.