Progression of Cancerous Tumors

A new method of examining cancerous tumors suggests that tumors may not evolve gradually, but rather in a punctuated or staccato-like bursts. The finding has shed new light on the process of tumor growth and metastasis, and may help in the development of new methods to clinically evaluate tumors.

Progression of Cancerous Tumors

The new analytic method, devised by Cold Spring Harbor Laboratory (CSHL) Professor Michael Wigler and colleagues, features a process called single cell sequencing (SNS), which enables accurate quantification of genomic copy number within a single cell nucleus. Genomic copy number refers to the amount of DNA in the nucleus. In cancer, portions of the genome are amplified or deleted, giving rise to extra or missing copies of key genes and interfering with mechanisms that normally control cell growth.

"We demonstrated that we can obtain accurate and high-resolution copy number profiles by sequencing a single cell from a cancerous tumor and that by examining multiple cells from the same cancer, we can make inferences about how the cancer evolved and spread," said Wigler. The CSHL team used two sampled tumors. Both were primary invasive breast cancer tumors of the so-called "triple-negative" type, generally regarded as the most aggressive form of breast cancer. One tumor sample was known from prior testing to be polygenomic: composed of distinct populations of tumor cells, whose number, genomic type and evolutionary history were not readily measurable using conventional techniques.