Strategies by which WWOX-deficient metastatic cancer cells utilize to survive via dodging, compromising, and causing damage to WWOX-positive normal microenvironment

Abstract

Proapoptotic tumor suppressor WWOX is upregulated in the early stage of cancer initiation, which probably provides limitation to cancer growth and progression. Later, WWOX protein is reduced to enhance cancer cell growth, migration, invasiveness and metastasis. To understand how WWOX works in controlling cancer progression, here we demonstrate that apoptotic stress mediated by ectopic WWOX stimulated cancer cells to secrete basic fibroblast growth factor (bFGF) in order to support capillary microtubule formation. This event may occur in the cancer initiation stage. Later, when WWOX loss occurs in cancer cells, hyaluronidase production is then increased in the cancer cells to facilitate metastasis. We determined that inhibition of membrane hyaluronidase Tyr216-phosphorylated Hyal-2 by antibody suppresses cancer growth in vivo. WWOX-negative (WWOX-) cells dodged WWOX+cells in the microenvironment by migrating individually backward to avoid physical contacts and yet significantly upregulating the redox activity of WWOX+parental cells or other WWOX+cell types for causing apoptosis. Upon detecting the presence of WWOX+cells from a distance, WWOX- cells exhibit activation of MIF, Hyal-2, Eph, and Wnt pathways, which converges to MEK/ERK signaling and enables WWOX- cells to evade WWOX+cells. Inhibition of each pathway by antibody or specific chemicals enables WWOX- cells to merge with WWOX+cells. In addition, exogenous TGF-β assists WWOX- cells to migrate collectively forward and merge with WWOX+cells. Metastatic WWOX- cancer cells frequently secrete high levels of TGF-β, which conceivably assists them to merge with WWOX+cells in target organs and secure a new home base in the WWOX+microenvironment. Together, loss of WWOX allows cancer cells to develop strategies to dodge, compromise and even kill WWOX-positive cells in microenvironment.

Pleiotropic tumor suppressor functions of WWOX antagonize metastasis

“…Moreover, a recent study showed that WWOX-deficient metastatic cells actively evade WWOX positive cells in their environment and then utilize various signaling pathways in order to force WWOX positive cells to undergo apoptosis, allowing further progression of metastasis. 40 These observations and others prompted us to further investigate possible roles of the tumor suppressor WWOX in cancer progression and metastasis.…”

Therapeutic Zfra4-10 or WWOX7-21 Peptide Induces Complex Formation of WWOX with Selective Protein Targets in Organs that Leads to Cancer Suppression and Spleen Cytotoxic Memory Z Cell Activation In Vivo

“…Naïve wild type Wwox B6 mice were treated with Zfra (1 mM in 100 μL PBS) once via tail vein injection, followed by resting for one week, and then were subjected to purification of activated Z cells in the spleen [ 6 , 7 ]. Activated Z cells (8 × 10 5 cells) were co-cultured with mouse breast 4T1 cell monolayers, in the presence of nuclear stains 4’,6-diamidino-2-phenylindole (DAPI; blue fluorescence) and propidium iodide (PI; red fluorescence), for imaging by time-lapse microscopy [ 9 , 10 , 13 , 16 , 25 ]. Activated spleen Z cells underwent clonal expansion and aggressively attacked and killed 4T1 cells ( Figure 7 A,B; Videos S1–S3 ).…”

“…It appears that the successful colonization of cancer cells is associated with their phenotypes and the host environment. We reported that when WWOX-negative cells encounter WWOX-positive cells, the WWOX-negative cells sense the presence of WWOX-positive cells from a distance (e.g., 500 μm) and undergo retrograde migration to avoid physical contacts—that is, these cells can no longer recognize each other, even though they are from the same cell lineage [ 25 ]. Loss of WWOX in cells allows them to acquire significantly increased mobility and migration.…”

“…The cells become alien to parental WWOX-positive cells [ 25 ]. In order to successfully colonize in a new WWOX-expressing organ, WWOX-negative metastatic cancer cells must partially kill a small portion of cells in the new host organ site and compromise with the host using TGF-β, so that they can successfully start docking and colonizing in the new home base [ 25 ]. Cultured cancer cells may not necessary be homogenous, as they mutate with time and the number of passages.…”

“…Cell sorting (FACSAria BD, Franklin Lakes, NJ, USA) was carried out to purify spleen activated Z cells. Activated Z cells (8 × 10 5 cells) were co-cultured with mouse breast 4T1 cell monolayers in the presence of nuclear stains 4’,6-diamidino-2-phenylindole (DAPI; blue fluorescence, Calbiochem, San Diego, CA, USA) and propidium iodide (PI; blue fluorescence, Invitrogen, Carlsbad, CA, USA) for imaging by time-lapse microscopy using an inverted Olympus IX81 microscope [ 9 , 10 , 13 , 16 , 25 ]. The extent of DAPI uptake by live cells indicates increases in nuclear membrane permeability and PI uptake for cell death [ 9 , 16 ].…”