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ALDH activity selectively defines an enhanced tumor-initiating cell population relative to CD133 expression in human pancreatic adenocarcinoma.

Kim MP, Fleming JB, Wang H, Abbruzzese JL, Choi W, Kopetz S, McConkey DJ, Evans DB, Gallick GE - PLoS ONE (2011)

Bottom Line: These cancer stem cells (CSCs), or tumor-initiating cells (TICs), exhibit properties of normal stem cells and are associated with resistance to current therapies.Although cell populations enriched for CD133 expression may alone possess tumorigenic potential, they are significantly less tumorigenic than ALDH(high) cell populations.We have thus identified a distinct population of TICs that should lead to identification of novel targets for pancreatic cancer therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America.

ABSTRACT

Background: Multiple studies in recent years have identified highly tumorigenic populations of cells that drive tumor formation. These cancer stem cells (CSCs), or tumor-initiating cells (TICs), exhibit properties of normal stem cells and are associated with resistance to current therapies. As pancreatic adenocarcinoma is among the most resistant human cancers to chemo-radiation therapy, we sought to evaluate the presence of cell populations with tumor-initiating capacities in human pancreatic tumors. Understanding which pancreatic cancer cell populations possess tumor-initiating capabilities is critical to characterizing and understanding the biology of pancreatic CSCs towards therapeutic ends.

Methodology/principal findings: We have isolated populations of cells with high ALDH activity (ALDH(high)) and/or CD133 cell surface expression from human xenograft tumors established from multiple patient tumors with pancreatic adenocarcinoma (direct xenograft tumors) and from the pancreatic cancer cell line L3.6pl. Through fluorescent activated cell sorting (FACs)-mediated enrichment and depletion of selected pancreatic cancer cell populations, we sought to discriminate the relative tumorigenicity of cell populations that express the pancreatic CSC markers CD133 and aldehyde dehydrogenase (ALDH). ALDH(high) and ALDH(low) cell populations were further examined for co-expression of CD44 and/or CD24. We demonstrate that unlike cell populations demonstrating low ALDH activity, as few as 100 cells enriched for high ALDH activity were capable of tumor formation, irrespective of CD133 expression. In direct xenograft tumors, the proportions of total tumor cells expressing ALDH and/or CD133 in xenograft tumors were unchanged through a minimum of two passages. We further demonstrate that ALDH expression among patients with pancreatic adenocarcinoma is heterogeneous, but the expression is constant in serial generations of individual direct xenograft tumors established from bulk human pancreatic tumors in NOD/SCID mice.

Conclusions/significance: We conclude that, in contrast to some previous studies, cell populations enriched for high ALDH activity alone are sufficient for efficient tumor-initiation with enhanced tumorigenic potential relative to CD133(+) and ALDH(low) cell populations in some direct xenograft tumors. Although cell populations enriched for CD133 expression may alone possess tumorigenic potential, they are significantly less tumorigenic than ALDH(high) cell populations. ALDH(high)/CD44(+)/CD24(+) or ALDH(low)/CD44(+)/CD24(+) phenotypes do not appear to significantly contribute to tumor formation at low numbers of inoculated tumor cells. ALDH expression broadly varies among patients with pancreatic adenocarcinoma and the apparent expression is recapitulated in serial generations of direct xenograft tumors in NOD/SCID. We have thus identified a distinct population of TICs that should lead to identification of novel targets for pancreatic cancer therapy.

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Histologic analysis of patient and direct xenograft tumors for expression of ALDH1.(A) Representative image demonstrating the histologic appearance of direct xenograft tumors established from freshly resected pancreatic tumors. Note tumor-gland formation and associated peri-tumoral stroma. (B) Comparison of ALDH1 expression in four different direct xenograft tumors to ALDH1 expression in original (parental) patient tumors. The pattern and location of ALDH1 expression is maintained during the xeno-transplantation process as reflected in derived xenograft tumors. An example of undetectable ALDH1 expression in both the patient tumor and derived direct xenograft is shown in the third panel from the top (MDA-PATX10). (C) Intra-tumoral heterogeneity of ALDH1 expression in direct xenograft tumors is readily identified as only a subset of luminal tumor cells demonstrate intense staining for ALDH1 relative to all other cells within tumor. Scale bar  = 125 µm (A), 180 µm (B), 125 µm (C).
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pone-0020636-g003: Histologic analysis of patient and direct xenograft tumors for expression of ALDH1.(A) Representative image demonstrating the histologic appearance of direct xenograft tumors established from freshly resected pancreatic tumors. Note tumor-gland formation and associated peri-tumoral stroma. (B) Comparison of ALDH1 expression in four different direct xenograft tumors to ALDH1 expression in original (parental) patient tumors. The pattern and location of ALDH1 expression is maintained during the xeno-transplantation process as reflected in derived xenograft tumors. An example of undetectable ALDH1 expression in both the patient tumor and derived direct xenograft is shown in the third panel from the top (MDA-PATX10). (C) Intra-tumoral heterogeneity of ALDH1 expression in direct xenograft tumors is readily identified as only a subset of luminal tumor cells demonstrate intense staining for ALDH1 relative to all other cells within tumor. Scale bar  = 125 µm (A), 180 µm (B), 125 µm (C).

Mentions: To expand tumor specimens available for study, we established a panel of direct xenograft tumors to provide sufficient specimens for the study and isolation of pancreatic cancer cell populations. As we have reported previously, minced patient tumors were heterotopically implanted into NOD/SCID mice [24]. Direct xenograft tumors were established from surgical specimens resected from 11 different patients with pancreatic adenocarcinoma as confirmed by final pathologic diagnosis. Tumors were derived from patients already treated with neoadjuvant therapy (chemotherapy and radiation) and from patients who had not received any neoadjuvant therapy as shown in Table 1. Once engrafted, tumors were grown to a maximum diameter of 1.2 cm and surgically procured for histologic evaluation and serial implantation into additional generations of NOD/SCID mice. The overall histologic appearances of direct xenograft tumors (and at least two subsequent passages of these tumors) were nearly identical to the original patient tumors. As shown in the representative H&E image in Figure 3A, tumor-gland formation and associated peri-tumoral stroma were evident in all direct xenograft tumors.


ALDH activity selectively defines an enhanced tumor-initiating cell population relative to CD133 expression in human pancreatic adenocarcinoma.

Kim MP, Fleming JB, Wang H, Abbruzzese JL, Choi W, Kopetz S, McConkey DJ, Evans DB, Gallick GE - PLoS ONE (2011)

Histologic analysis of patient and direct xenograft tumors for expression of ALDH1.(A) Representative image demonstrating the histologic appearance of direct xenograft tumors established from freshly resected pancreatic tumors. Note tumor-gland formation and associated peri-tumoral stroma. (B) Comparison of ALDH1 expression in four different direct xenograft tumors to ALDH1 expression in original (parental) patient tumors. The pattern and location of ALDH1 expression is maintained during the xeno-transplantation process as reflected in derived xenograft tumors. An example of undetectable ALDH1 expression in both the patient tumor and derived direct xenograft is shown in the third panel from the top (MDA-PATX10). (C) Intra-tumoral heterogeneity of ALDH1 expression in direct xenograft tumors is readily identified as only a subset of luminal tumor cells demonstrate intense staining for ALDH1 relative to all other cells within tumor. Scale bar  = 125 µm (A), 180 µm (B), 125 µm (C).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3113804&req=5

pone-0020636-g003: Histologic analysis of patient and direct xenograft tumors for expression of ALDH1.(A) Representative image demonstrating the histologic appearance of direct xenograft tumors established from freshly resected pancreatic tumors. Note tumor-gland formation and associated peri-tumoral stroma. (B) Comparison of ALDH1 expression in four different direct xenograft tumors to ALDH1 expression in original (parental) patient tumors. The pattern and location of ALDH1 expression is maintained during the xeno-transplantation process as reflected in derived xenograft tumors. An example of undetectable ALDH1 expression in both the patient tumor and derived direct xenograft is shown in the third panel from the top (MDA-PATX10). (C) Intra-tumoral heterogeneity of ALDH1 expression in direct xenograft tumors is readily identified as only a subset of luminal tumor cells demonstrate intense staining for ALDH1 relative to all other cells within tumor. Scale bar  = 125 µm (A), 180 µm (B), 125 µm (C).
Mentions: To expand tumor specimens available for study, we established a panel of direct xenograft tumors to provide sufficient specimens for the study and isolation of pancreatic cancer cell populations. As we have reported previously, minced patient tumors were heterotopically implanted into NOD/SCID mice [24]. Direct xenograft tumors were established from surgical specimens resected from 11 different patients with pancreatic adenocarcinoma as confirmed by final pathologic diagnosis. Tumors were derived from patients already treated with neoadjuvant therapy (chemotherapy and radiation) and from patients who had not received any neoadjuvant therapy as shown in Table 1. Once engrafted, tumors were grown to a maximum diameter of 1.2 cm and surgically procured for histologic evaluation and serial implantation into additional generations of NOD/SCID mice. The overall histologic appearances of direct xenograft tumors (and at least two subsequent passages of these tumors) were nearly identical to the original patient tumors. As shown in the representative H&E image in Figure 3A, tumor-gland formation and associated peri-tumoral stroma were evident in all direct xenograft tumors.

Bottom Line: These cancer stem cells (CSCs), or tumor-initiating cells (TICs), exhibit properties of normal stem cells and are associated with resistance to current therapies.Although cell populations enriched for CD133 expression may alone possess tumorigenic potential, they are significantly less tumorigenic than ALDH(high) cell populations.We have thus identified a distinct population of TICs that should lead to identification of novel targets for pancreatic cancer therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America.

ABSTRACT

Background: Multiple studies in recent years have identified highly tumorigenic populations of cells that drive tumor formation. These cancer stem cells (CSCs), or tumor-initiating cells (TICs), exhibit properties of normal stem cells and are associated with resistance to current therapies. As pancreatic adenocarcinoma is among the most resistant human cancers to chemo-radiation therapy, we sought to evaluate the presence of cell populations with tumor-initiating capacities in human pancreatic tumors. Understanding which pancreatic cancer cell populations possess tumor-initiating capabilities is critical to characterizing and understanding the biology of pancreatic CSCs towards therapeutic ends.

Methodology/principal findings: We have isolated populations of cells with high ALDH activity (ALDH(high)) and/or CD133 cell surface expression from human xenograft tumors established from multiple patient tumors with pancreatic adenocarcinoma (direct xenograft tumors) and from the pancreatic cancer cell line L3.6pl. Through fluorescent activated cell sorting (FACs)-mediated enrichment and depletion of selected pancreatic cancer cell populations, we sought to discriminate the relative tumorigenicity of cell populations that express the pancreatic CSC markers CD133 and aldehyde dehydrogenase (ALDH). ALDH(high) and ALDH(low) cell populations were further examined for co-expression of CD44 and/or CD24. We demonstrate that unlike cell populations demonstrating low ALDH activity, as few as 100 cells enriched for high ALDH activity were capable of tumor formation, irrespective of CD133 expression. In direct xenograft tumors, the proportions of total tumor cells expressing ALDH and/or CD133 in xenograft tumors were unchanged through a minimum of two passages. We further demonstrate that ALDH expression among patients with pancreatic adenocarcinoma is heterogeneous, but the expression is constant in serial generations of individual direct xenograft tumors established from bulk human pancreatic tumors in NOD/SCID mice.

Conclusions/significance: We conclude that, in contrast to some previous studies, cell populations enriched for high ALDH activity alone are sufficient for efficient tumor-initiation with enhanced tumorigenic potential relative to CD133(+) and ALDH(low) cell populations in some direct xenograft tumors. Although cell populations enriched for CD133 expression may alone possess tumorigenic potential, they are significantly less tumorigenic than ALDH(high) cell populations. ALDH(high)/CD44(+)/CD24(+) or ALDH(low)/CD44(+)/CD24(+) phenotypes do not appear to significantly contribute to tumor formation at low numbers of inoculated tumor cells. ALDH expression broadly varies among patients with pancreatic adenocarcinoma and the apparent expression is recapitulated in serial generations of direct xenograft tumors in NOD/SCID. We have thus identified a distinct population of TICs that should lead to identification of novel targets for pancreatic cancer therapy.

Show MeSH
Related in: MedlinePlus