Induction of metastatic cancer stem cells from the NK/LAK-resistant floating, but not adherent, subset of the UP-LN1 carcinoma cell line by IFN-γ

Abstract

As an advanced status of cancer stem cells (CSCs), metastatic CSCs (mCSCs) have been proposed to be the essential seeds that initiate tumor metastasis. However, the biology of mCSCs is poorly understood. In this study, we used a lymph node (LN) metastatic CEA-producing carcinoma cell line, UP-LN1, characterized by the persistent appearance of adherent (A) and floating (F) cells in culture, to determine the distribution of CSCs and mechanisms for the induction of mCSCs. F and A cells displayed distinct phenotypes, CD44(high)/CD24(low) and CD44(low)/CD24(high), respectively. The CSC-rich nature of F cells was typified by stronger expression of multiple drug resistance genes and a 7.8-fold higher frequency of tumor-initiating cells in NOD/SCID mice when compared with A cells. F cells showed a greater depression in HLA class I expression and an extreme resistance to NK/LAK-mediated cytolysis. Moreover, the NK/LAK-resistant F cells were highly susceptible to IFN-γ-mediated induction of surface CXCR4, with concomitant downregulation of cytoplasmic CXCL12 expression, whereas these two parameters remained essentially unchanged in NK/LAK-sensitive A cells. Following the induction of surface CXCR4, enhanced migratory/invasive potential of F cells was demonstrated by in vitro assays. Confocal immunofluorescence microscopy showed the two distinct phenotypes of F and A cells could be correspondingly identified in monodispersed and compact tumor cell areas within the patient's LN tumor lesion. In response to IFN-γ or activated NK/LAK cells, the CXCR4(+) mCSCs could be only induced from the CSCs, which were harbored in the highly tumorigenic CD44(high)/CD24(low) F subset. Our results revealed the complexity and heterogeneity of the CSC of this cell line/tumor and the differential immunomodulatory roles of F and A cells. A better understanding of the interactions among different classes of CSCs and their niches may assist us in eradicating the CSCs/mCSCs through targeted immunotherapy, chemotherapy, or both.

Strategies for Isolating and Enriching Cancer Stem Cells: Well Begun Is Half Done

“…Similarly, the CD44 hi CD24 lo population has also been found to be more immunoresistant in other breast cancer cell lines, such as SK-BR3, MDA-MB-231, and BT474 cells. Recently, CXCR4 + metastatic CSCs were shown to be induced by interferon-g (IFN-g) from NK resistant CSCs harbored in the highly tumorigenic CD44 hi CD24 lo subset [208]. Thus, a novel strategy based on immunoselection with NK cells could be used to isolate and enrich CSCs from cancer cell populations [209].…”

Differential expression of CD44 and CD24 markers discriminates the epitheliod from the fibroblastoid subset in a sarcomatoid renal carcinoma cell line: evidence suggesting the existence of cancer stem cells in both subsets as studied with sorted cells

“…This subpopulation, referred to as CSCs or tumor-initiating cells (TICs), has the ability to self-renew and give rise to differentiated progenies of cancer cells that contribute to tumor initiation and reestablish tumor heterogeneity [10]. Several studies indicate that CSCs might cause resistance to chemotherapy and radiotherapy [12] and cell-based immunotherapeutic effectors [13]. Putative CSCs have been identified in several human tumors based on the expression of a specific molecule or combination of molecules (e.g., CD133, CD44, CD166, aldehyde dehydrogenases), including the first identified acute myeloid leukemia [14], and a few solid tumors such as brain [15], breast [16], gastrointestinal [13] and prostate cancer [17].…”

Immunotherapy of cancer is a part of biotherapy

“…Most recently, the successful identification of two cellular entities, namely cancer stem cells (CSCs) and metastatic cancer stem cells (mCSCs) with the expression of CXCR4 [21,32] , both constituted very small proportions of cells within a given tumor, has stimulated a new direction for investigations as to how to eradicate or control of these two cell types. Of note, the CXCR4-positive mCSCs with metastatic potential constitute much lower numbers than the tumoroigenic CSCs in the given tumor [32,33] . This is because both entities are considered the root causes of cancer (tumorigenesis), with the latter being the cause of both tumorigenic and metastatic activities.…”

“…These non-CSCs are believed to be more sensitive to be killed by conventional therapies, such as radiation and chemotherapy. Expression of surface antigens such as ALDH, CD44, EpCAM, or CD133, which distinguish CSCs from non-CSC tumor cells and normal counterpart cells, together with CSC immunogenicity and relatively low toxicity of immunotherapies, makes immunotargeting of CSCs/mCSCs a promising approach for cancer biotherapy [32][33][34][35] . The approaches to target and eliminate CSCs include using NK, DCs, T cells, mAbs, and bispecific antibodiess.…”