Cancer Dormancy 8/28/08

Does Tumor dormancy Exist? 20-45% of breast cancer and prostate cancer will relapse years or decades later after initial tumor removal – can not be explained by continuous tumor cells proliferation – dormancy makes sense ; Disseminated/cirulating cancer cells (DTCs, CTCs) can be detected in 30% of breast cancer patients at the time of diagnosis in a large study with 4703 patiens; In some studies, all CTCs identified after surgery are negative for Ki67 staining; Aguirre-Ghiso JA, 2007, Nature Review Cancer; Braun S et al, 2005, NEJM; Muller V et al, 2005, Clin Cancer Res

In mouse models, dormancy certainly exists. With better technology, you can find them and follow them too. Does Tumor dormancy Exist? Macro-metastasisMicro-metastasis M4A462% mice form mets from orthotopic tumor Single cells, to 1-4 cell culsters, mean 73 micro- can persist upto 6 months NM2C50%Single to 1-4 cells, mean 50 Can be recovered as proliferating cells in vitro; still tumorigenic in vivo at s.c and fat pad(better), and still only form micro- mets Goodison S, et al, 2003, Clin Cancer Res M NM

MPIO(micron-sized iron oxide particle)-label GFP tagged MDA- MB-231BR cells; Inject into left ventricle of mouse Monitor tumor cells in the brain with MRI. Fate of the cells Heyn C et al, 2006, Mag Res Medicine

Cancer Dormancy Cellular dormancy: cells probably enter G0 –G1 arrest – cells are truly inactive Tumor mass dormancy: cell proliferation is counterbalanced by apoptosis due or poor vasculature or immune response to the tumor cells cells are still active, just tumor as a mass can not expand beyond certain size.

Potential mechanisms Tumor cells fail to recognize the environment, therefore disrupting crosstalk between growth factor signaling and adhesion signaling. G0-G1 arrest differentiation senescence? Immunosurveillance Tumor cells fail to recruit blood vessles.

Microenvironment – story #1 integrin beta1 Weaver VM et al, 1997, JCB Nonmalignant Tumorigenic 3-DIntegrin beta 1E-cad After days in matrigel:

S-1T4-2 IgGT4-2 beta1 blocking Ab E-cad beta-cat F-actin nuclei Weaver VM et al, 1997, JCB Reversible!

When tumor cells fail to engage integrin signaling (fail to talk with ECM), cells can assume a differentiated phenotype, and undergo growth arrest through induction of p21 cip. In vitro – nothing to do with metastasis per se

Microenvironment – story #2 integrin beta 1 White DE et al, 2004, cancer cell

Conclusion In the primary tumor setting: Inactivation of integrin (fail to communicate with ECM) render epithelial cells dormant – persist in the tissue but fail to proliferate in vitro. These data hint that failure to engage integrin signaling allows the cells to either differentiate or become dormant. Not clear if true in metastatic dormant cells. Not shown in patients.

Microenvironment – story #3 uPAR Reduce uPAR expression Expected: reduced invasion Unexpected: tumor become dormant for a while Although in vitro proliferation is not affected. Yu W et al, 1997,JCB

Similar % live or dead cells Much reduced proliferating cells when reducing uPAR Yu W et al, 1997,JCB

Met cells have strong ERK activation but not uPAR- low cells Soluble uPA activates ERK pathway –time/conc.-dep Adhesion on FN associates with expression level of uPAR, although no diff. in surface expression level of alpha5 beta1 Aguirre-Ghiso et al, 1999 JCB, 2001 MCB

Co-IP of uPAR and beta1 integrin Reduced pERK if disrupt uPAR and integrin interaction using peptide. ERK Aguirre-Ghiso et al, 1999 JCB, 2001 MCB

conclusions Using cell lines that either metastasize or remain dormant in chick CAM: uPAR seems to activated integrin (low uPAR, integrins are there but not as active), to “talk” with ECM. This induces strong ERK signaling. Fits the idea that diminished “talk” with the microenvironment renders the cells domant. Patients: uPAR is a poor prognostic marker for breast, lung, colon, esophageal and gastric cancer.

Microenvironment – story #4 CD82-DARC interaction as metastasis suppressor DARC expression – vessels only AT6.1-vector AT6.1-KAI1 Prostate cancer interact with endothelial cells in KAI-1 dependent manner Bandyopadhyay S et al, 2006, Nature Med

Interaction between KAI1 and DARC results in reduced proliferation in prostate cancer cell line No diff. in primary tumor growth Less met from DARC +/+ or +/- mice

Senescence? Probably by down- TBX2 and up p21 Cip

Conclusion Suggests endothelial cells can function as one of the metastasis-suppressive mechanism that contribute to upregulation of p21 Cip and reduction of tumor cell proliferation.- dormant Maybe senenscence?

Microenvironment – story #5 Secreted Kiss function as metastasis suppressor Conditioned medium Full-length No signal sequence – not secreted C human melanoma cells Secreted Kiss blocks metastasis (iv model), but not non-secreted form

Cells expressing Kiss persist in the lung for at least 120days but fail to manifest into full mets – induces dormancy in the cells?

In these melanoma cells, could not detect the receptor GPR54. See strong systemic anti-metastasis effect – other organs: kidney, eye, bone. So maybe (just maybe) secreted Kiss function through other common cells in the microenvironment? (or different receptor on the cells) Extra information and hypothesis

What is the cellular machinery that allows the cells undergo dormancy? p38 ERK Stress!! Oncogenic

T-HEp3D-HEp3LK25AS24DormantMeta. High p38 signaling correlates low ERK signaling in these cells Aguirre-Ghiso et al, 1999 JCB, 2001 MCB

Aguirre-Ghiso et al, 2004, Cancer Research ERK reporter p38 reporter

In another study by Rinker-Schaeffer’s group, identify JNKK1/MKK4 and MKK7 as metastasis suppressor – using prostate cancer cell lines. Fits broadly in the idea that stress signal may suppress tumor cells colonization.

Mechanisms regulating cellular dormancy… Environment: Tumor - ECM interactions: integrin activation  ERK vs p38 Tumor cells – vasculature interaction Tumor cells – others?

Other speculations??? How about contact inhibition? Normal organ size control; Cells retreat to G0-G1 arrest And in fact, dissemination probably occurs early (as well as later) during primary tumor formation Clues from other organism? Worms undergo diapause when the environment is not suitable – p38 (sensing oxidative stress) induces diapause; ER stress signal; DAF and IGF1 involved in diapuse… Plant seeds undergo dormancy.

Tumor mass dormancy Immunosurveillance - been shown in B cell lymphoma mouse model Angiogenic dormancy