We identified circulating CD8+ T-cell populations specific for the tumor-associated antigens (TAAs) MART-1 (27-35) or tyrosinase (368-376) in six of eleven patients with metastatic melanoma using peptide/HLA-A*0201 tetramers. These TAA-specific populations were of two phenotypically distinct types: one, typical for memory/effector T cells; the other, a previously undescribed phenotype expressing both naive and effector cell markers. This latter type represented more than 2% of the total CD8+ T cells in one patient, permitting detailed phenotypic and functional analysis. Although these cells have many of the hallmarks of effector T cells, they were functionally unresponsive, unable to directly lyse melanoma target cells or produce cytokines in response to mitogens. In contrast, CD8+ T cells from the same patient were able to lyse EBV-pulsed target cells and showed robust allogeneic responses. Thus, the clonally expanded TAA-specific population seems to have been selectively rendered anergic in vivo. Peptide stimulation of the TAA-specific T-cell populations in other patients failed to induce substantial upregulation of CD69 expression, indicating that these cells may also have functional defects, leading to blunted activation responses. These data demonstrate that systemic TAA-specific T-cell responses can develop de novo in cancer patients, but that antigen-specific unresponsiveness may explain why such cells are unable to control tumor growth.

The question whether tumorigenic cancer stem cells exist in human melanomas has arisen recently1. Here we show that in melanomas, tumor stem cells (MTSC) can be isolated prospectively as a highly enriched CD271+ MTSC population using a process that maximizes viable cell transplantation1,6. In this study the tumors sampled were taken from a broad spectrum of sites and stages. High viability FACS isolated cells resuspended in a matrigel vehicle were implanted into T, B, and NK deficient Rag2−/− γc−/− mice (RG) mice. The CD271+ subset of cells was the tumor initiating population in 9/10 melanomas tested. Transplantation of isolated melanoma cells into engrafted human skin or bone in RG mice resulted in melanoma from CD271+ but not CD271− cells. We also showed that tumors transplanted by CD271+ patient cells were capable of metastasis in-vivo. Importantly, CD271+ melanoma cells lacked expression of TYR, MART and MAGE in 86%, 69% and 68% of melanoma patients respectively suggesting why T cell therapies directed at these antigens usually result in only temporary tumor shrinkage.

From 1970 to 1985, 663 patients underwent curative resection of colon and rectal adenocarcinomas. All surgical specimens were examined for tumor "budding," defined as small clusters of undifferentiated cancer cells ahead of the invasive front of the lesion. Patients were divided into two groups according to degree of budding: none or mild (BD-1) and moderate or severe (BD-2). BD-1 occurred in 493 patients (74.4 percent), and BD-2 was found in 170 patients (25.6 percent). More severe budding was associated with worse outcome: 71.1 percent of BD-2 patients had recurrence, compared with 20.0 percent of BD-1 patients (P < 0.005). The five-year survival rate was worse in BD-2 than in BD-1 (22.2 percent vs. 70.7 percent; P < 0.001). The 10-year survival rate was also worse in BD-2 than in BD-1 (13.8 percent vs. 50.6 percent; P < 0.001). The incidence of BD-2 rose with the Dukes stage. However, the five-year survival rate of Dukes B patients with BD-2 lesions was worse than that of Dukes C patients with BD-1 cancers (29.1 percent vs. 66.2 percent; P < 0.001). Moreover, there was no difference in five-year survival among BD-1 patients with either Dukes B or C lesions (68.3 percent vs. 66.2 percent). The presence of more severe budding appears to indicate a vigorous biologic activity of colorectal cancer. Thus, meticulous follow-up--and possibly adjuvant chemotherapy--may be beneficial for patients with marked budding, regardless of their Dukes stage.