In 1889 Stephen Paget came up with the ‘seed to soil’ theory to explain why some cancers seem to spread to specific organs, rather than just invading the body at random. He said that perhaps there were features of the soil (the organ) that determined whether the seed (the cancer) took root there. Some soils simply aren’t hospitable to some seeds (having gardened in the heavy red clay of North Carolina, I can attest to that…)
Quite a few speakers evoked the seed to soil theory in talks about metastasis. One such speaker, Sara Sukumar of Johns Hopkins University, mentioned it while talking about her rapid autopsy program. The program is meant to test the assumption that the characteristics of the original ‘primary’ tumour will be shared by its metastatic offspring. There is some evidence to support this: gene expression patterns in some breast cancer tumours have been shown to resemble gene expression in their distant metastases, for example. But Sukumar says our understanding of this relationship is hindered by a lack of tissue to study because researchers often have only a single biopsy from each patient.
So Sukumar has a rapid autopsy program to collect tumour samples. The autopsy starts within four hours of when the patient died. She and her colleagues can then study features of the tumours to see if they express the same hormone receptors or other molecular markers. They create cell cultures of the tumours and inject tumour tissue into mice to study their growth. So far they’ve only done the autopsies on 18 patients, but Sukumar says she’s found a lot of variation between secondary tumours and the original biopsy. One questioner pointed out that there can be a long time (decades even) between the original biopsy and death of the patient, giving the tumours plenty of time to change. But overall, the system sounds like a promising way to look at the relationship between seed and soil.