The critical roles of tumor-initiating cells and the lymph node stromal microenvironment in human colorectal cancer extranodal metastasis using a unique humanized orthotopic mouse model.

Colorectal cancer (CRC) is the second-most common cause of cancer-related mortality. The most important prognostic factors are lymph node (LN) involvement and extranodal metastasis. Our objective is to investigate the interactions between CD133(+)CXCR4(+) (CXC receptor 4) colorectal cancer tumor-initiating cells (Co-TICs) and the LN stromal microenvironment in human CRC extranodal metastasis. We established a unique humanized orthotopic xenograft model. Luciferase-tagged CRC cell lines and human cancer cells were injected intrarectally into nonobese diabetic/SCID mice. Mesenteric LN stromal cells, stromal cell line HK, or CXCL12 knockdown HK (HK-KD-A3) cells were coinoculated with CRC cells. Tumor growth and metastasis were monitored by bioluminescent imaging and immunohistochemistry. We found that this model mimics the human CRC metastatic pattern with CRC cell lines or patient specimens. Adding LN stromal cells promotes CRC tumor growth and extranodal metastasis (P < 0.001). Knocking down CXCL12 impaired HK cell support of CRC tumor formation and extranodal metastasis. When HK cells were added, sorted CD133(+)CXCR4(+) Co-TICs showed increased tumor formation and extranodal metastasis capacities compared to unseparated and non-Co-TIC populations. In conclusion, both Co-TIC and LN stromal factors play crucial roles in CRC metastasis through the CXCL12/CXCR4 axis. Blocking Co-TIC/LN-stromal interactions may lead to effective therapy to prevent extranodal metastasis.

CD 133+ and CXCR4+ colon cancer cells as a marker for lymph node metastasis.

INTRODUCTION: Colorectal cancer (CRC) stem cells or tumor-initiating cells (Co-TIC) are implicated in both cancer recurrence and extranodal metastasis. CD133 and CXCR4 are specific cell surface markers that are indicators of Co-TIC. The presence of lymph node (LN) metastases is one of the strongest negative prognostic factors for CRC patients. We examined the relationship between the Co-TIC markers CD133 and CXCR4 and LN involvement in CRC. METHODS: CRC cells were isolated via enzymatic digestion. CD133(+), CXCR4(+), and double-positive CRC cells were detected by fluorescence-activated cell sorting analysis. The percentages of CD133(+), CXCR4(+), and double-positive cells were identified and correlated to the number and percentage of positive LN on staging. RESULTS: Twenty-seven samples underwent fluorescence-activated cell sorting analysis. The mean percentage of CD133(+) cells was 3.94% (range 0.15%-19.06%). The mean percentage of CXCR4(+) cells was 6.15% (range 0%-27.11%). The mean percentage of CD133(+)CXCR4(+) cells was 0.45% (range 0%-2.08%). Thirteen patients had LN metastasis: 8 N1 disease and 5 N2 disease. The correlation coefficients between the percentage of Co-TIC marker-positive cells and percentage of positive LN were r = 0.58 (P = 0.0016) for CD133(+) cells, r = 0.36 (P = 0.5868) for CXCR4(+) cells, and r = 0.56 (P = 0.0022) for double-positive cells. DISCUSSION: Our results show CD133(+) and CD133(+)CXCR4(+) cancer cells correlate with the presence of LN metastasis in CRC. Further studies will examine whether these markers can give consistent prognostic information and may help to develop novel diagnostic and therapeutic options.

Lymph node stromal cells enhance drug-resistant colon cancer cell tumor formation through SDF-1α/CXCR4 paracrine signaling.

Colorectal cancer (CRC) is the third most common malignancy and the second leading cause of cancer-related deaths in America. Nearly two thirds of newly diagnosed CRC cases include lymph node (LN) involvement, and LN metastasis is one of the strongest negative prognostic factors for CRC. It is thought that CRC tumors contain a small population of drug-resistant CRC tumor-initiating cells (Co-TICs) that may be responsible for cancer recurrence. To evaluate the effects of the LN stromal cells on Co-TICs, we established a unique xenoplant model using CRC cells isolated by enzymatic digestion from consented patient specimens, HT-29 cells, HCA-7 cells, and LN stromal cell line HK cells. We found that HK cells and HK cell-conditioned media enhanced CRC tumor formation and tumor angiogenesis. Cells expressing CD133(+) and the stromal cell-derived factor 1α (SDF-1α) receptor CXCR4 were enriched in chemotherapeutic-resistant CRC cells. CD133(+)CXCR4(+) Co-TICs isolated from patient specimens are more tumorigenic than unsorted tumor cells. Furthermore, the inhibitors specific to HK cell-derived SDF-1α reduced tumor formation and tumor angiogenesis. Our results have demonstrated a role for Co-TICs in tumor growth and defined the influence of LN stromal cells on Co-TICs. We have identified a major Co-TIC/LN microenvironment-specific mechanism for CRC resistance to chemotherapeutic agents and established experimental platforms for both in vitro and in vivo testing, indicating that SDF-1α and its receptor, CXCR4, may be targets for clinical therapy.