Quiescent cancer cells are those in the resting phase, i.e. G0. They will start growing when the general environment (nutrients esp) becomes favorable and their machinery for growth and division has recovered. Starvation without malnutrition may keep many tumours quiescent. Dormancy is when a special trigger is required for growth; it may be considered as a special case of quiescence.  Clinically (and of course in the lab) this would be most applicable to Hormone dependent tumours. Quiescence is related to the words acquiesce, quiet, etc. and dormant related to sleep. OK?

thanks so much dr. Narayanan. So, tumor cells when they are in latency period and triggered by, for example, a chemotherapeutic agent  for entering the cell cycle, they were originally in dormancy. But if the tumor cells in latency period switched to a proliferative state because their environment improved, for example, immunosuppression occurs, they were in Quiescence. Right?

Bringing in Chemotherapy, immunology etc., complicates things. I think it is best to reserve the term dormant for tumours/conditions wherein the cells have undergone malignat transformation but have not yet started growing as a tumour. A trigger event may start the growth at any time and no one really knows what this is; it may even be that body's immunological system is constantly removing them (Remember Burnets theory of immunosurveillance? see http://www.jleukbio.org/content/84/4/988.full). It may likened to a seed, which is dormant but starts growing once it gets water. Therefore, they are unlikely to be given any chemo/radiotherapy and the first part of the question is really not applicable. Now in an established tumour, there may be many (or all cells) in Q/G0 state. In such a case therapy will result in killing of the dividing cells which are generally more sensitive to therapy. Then the cells in Q will start growing; i.e. they are recruited into growth. Since total number of cells are low, the growth fraction (GF) increases. That is why in both chemotherapy and radiotherapy keeping to the planned therapy schedule and avoiding interruptios is very very important. There is another scenario. The body may be having latent/dormant metastasis which may start growing after treatment for the primary, unless these too are covered by treatment. This may be because of nutrition alteration, immuneity imbalance (In old days we used to learn that the primary secreted Tumor Associate Antigens (TAA) which incresed immunity against them and kept the metastasis at bay; but once the source of the TAA was removed the immunity became lax, allowing the metastasis to grow. I dont know if this view is subscribed to now.  For further reading I suggest http://www.translational-medicine.com/content/3/1/8 or http://jrr.oxfordjournals.org/content/43/1/11.full.pdf. Hope this is sufficient for stsrters

I think dormant cells are cells in quiescent stage i.e. G0 phase. And this dormant cells are main reason for tumor recurrence. Chemotherapy only eliminates rapidly diving and proliferating cells and they do not kill dormant cells as they are in quiescent stage. Once condition become favorable or some growth factors induces changes they again start proliferation and form tumors.

Saying that Dormant cells are in quiescent stage is like saying that they mean the same. It is basically a question of accepted definitions. I think the term Quiscent cells was first used by Dr. Mendelsohn, past Director of MD Anderson Hospital, to define a tumour population, such that P (GF)=P/P+Q where P is proliferating and Q is non-proliferating cells. The Q cells are cells in G0 or resting phase. The term dormancy is better applicable to the tumour as a whole, the in a tumour if the cell loss=cell renewal, the tumour as a whole will stay same number and in initial stages, ie before detection, it will remain apparently dormant. Tumours in many premalignant conditions may be dormant. In the case of individual tumour cells, if they are in a stage between normalcy and malignancy (a premalignant cell) then also the cell itself may be considered as having dormant malignancy.

An analogy may be helpful. In children their sexuality is dormant where as in adults it remains quiscent when not active.

Following the accepted definitions is best. Q cells do have an accepted definition as outlined above.

Narayanan

Dear Narayanan,

Would you be so kind in providing me with TWO specific markers of G0-CANCER cell phase? Along with "solid" scientific-related articles ...

In my humble opinion, the "modern" cancer biology research about "quiescent cancer cells" relates to (a choice at randon from my own choice) articles as those here attached ... but in which I failed to find actually reliable markers of G0-related cancer cells.

Best regards

Robert

Dear Shimaa Shehata,

Find in attached file a wonderful book about your question.

Agreed with Narayanan on the point that dormancy is a term that refers to the tumor as a whole, whereas quiescence happens to an individual cell. Here's a nice paper asking the question on whether tumor dormancy is due to cellular quiescence (tumor is basically static) vs balanced proliferation (tumor may have a lot of activity but death and proliferation happen at similar rates as to make the tumor appear static). http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3702639/

Thank you Jill.

Dear Robert, sorry for the delay. Actually I am not much involved in cancer research now. I don't think there is any marker for G0 since it is in an inactive state. If a cell doesn't have markers if activity, such as DNA synthesis like radiolabelled uptake or other markets if division such a Ki67 etc., then that particular cell or group of cells may be presumed to be in G0, I think!

Narayanan