Stem cells and their implications for colorectal cancer

Abstract

The colonic crypt is home to several multipotent stem cells. These stem cells reside in a niche at the base of the crypt, which controls their behavior and maintains the stem cell's homeostasis through a variety of signaling pathways and interactions. Several attempts have been made to define markers that can identify colonic stem cells, the most useful of which is Lgr5, a Wnt target gene. Although the crypt base contains several stem cells, each colonic crypt comprises a single clone of cells. Investigators have attempted to reconcile these apparently contradictory observations by conducting research into stem cell division. The propagation of stem-cell-acquired mutations through a crypt results in a monocryptal adenoma that, through crypt fission, develops into a microadenoma. Some early adenomas become polyclonal through an as yet unknown mechanism. The discovery of subpopulations of cancer cells that can initiate tumors when implanted into mice has renewed interest in the existence of cancer stem cells, especially with regard to their implications for the use of chemotherapy. Various potential markers of cancer stem cells have been investigated, particularly CD133, but the cancer stem cell theory still has some limitations.

Analysis of immunoexpression of common cancer stem cell markers in ameloblastoma

“…Recurrence may be in part due to the existence of CSCs. Growing evidence suggests that human cancers are stem cell diseases, and only a small subpopulation of cancer cells, endowed with stem cell-like features, may be responsible for tumor initiation and progression (17). Novel strategies for successful tumor treatment should focus on the elimination of CSCs.…”

Lgr5 and Lgr6 as markers to study adult stem cell roles in self-renewal and cancer

“…Many other markers of the þ 4 and CBC small intestinal stem cell compartments have been proposed over the last decade, including Prominin1, mTert, Musashi1, DcamKL1 and Sox9 (for comprehensive reviews see Lin and Barker, 2011;Zeki et al, 2011).…”

Gene expression profiles of tumor regression grade in locally advanced rectal cancer after neoadjuvant chemoradiotherapy

“…Hence, it is possible that gene expression correlated with TRG might reflect the characteristics, including resistance to CRT, of residual cancer cells and might be associated with prognosis in patients with rectal cancer after pre-operative CRT. DNA repair pathways (9), cell cycle pathways (10), hypoxia (11,12), anti-apoptosis (13) and cancer stem cells (14,15) have been implicated in the mechanisms of CRT resistance. Twenty genes were selected for a comparison in expression levels between CRT responders and non-responders: PCNA and MKI67 (Ki67) as proliferative markers; CDKN1A (p21…”