The Cause of Treatment Resistance in Small Cell Lung Cancer: TUMOROSPHERES

Small cell lung cancer accounts for a proportion of all lung cancersamounting to 15%; it originates particularly in the lung’s endocrine cells and tends to grow and spread rapidly. As with most rapidly growing and spreading cancers, its most effective treatment is chemotherapy. However, the main difficulty in treating small cell lung cancer is the development of resistance to chemotherapy. In patients with advanced small cell lung cancer, the tumor usually recurs (relapses) 1 year after successful responses to chemotherapy and radiotherapy and becomes resistant to chemotherapy. The disease then progresses more rapidly. Studies in recent years have sought to understand the causes of drug resistance in small cell lung cancer cells. A study published in July 2017 discovered that circulating tumor cells join together to form chemotherapy-resistant structures . In the research, circulating tumor cells were isolated from a patient, and their responses to chemotherapy drugs were examined.

According to the findings:

• Circulating tumor cells were observed to form tumorospheres , protecting themselves from chemotherapy and thereby causing drug resistance.
• These structures were found to contain thousands of cells and to exhibit 8 times greater resistance to chemotherapy drugs .
• The main reason for this is that tumor cells slow down their growth, allowing them to evade chemotherapy that targets rapidly dividing cells.

What Does This Study Mean for Cancer?

• This is the first study in which circulating tumor cells from patients with stage 4 small cell lung cancer were isolated and grown in the laboratory.
•  After approximately 30 years of uncertainty, one of the underlying causes of chemotherapy resistance in small cell lung cancer has been clarified.
• More detailed investigation of tumorospheres and the development of enzymes and inhibitors to break up these structures could pave the way for effective cancer treatments.
• It must be emphasized that there is no FDA approval for the use of circulating tumor cells in the early diagnosis of cancer. However, studies suggest that these cells play a role in drug resistance in cancer and in metastasis . Future studies will improve our understanding of circulating tumor cells.