# The Rare, Fixed Cancer Stem Cell Hierarchy: research update

Dated 5 October 2026. Local prepublication addendum; archived grade unchanged.

Functional hierarchies and relapse-sustaining cell states occur in particular tumours. Permissive transplantation and lineage-resolved state switching challenge a universal rare, fixed and irreplaceable compartment.

## Research timeline

Electronic year is used where recorded; issue year is retained in each source card. The chronology is selected, not exhaustive, and does not establish priority or causation.

| Year | Primary study | Design and finding | Inference limit |
|---|---|---|---|
| 1997 | [Human acute myeloid leukemia is organized as a hierarchy that originates from a primitive hematopoietic cell.](https://pubmed.ncbi.nlm.nih.gov/9212098/) | Human AML xenotransplantation. A prospectively isolated compartment serially generated heterogeneous leukemia. | Transplantation sufficiency depends on host and assay; endogenous universal necessity is separate. |
| 2003 | [Prospective identification of tumorigenic breast cancer cells.](https://pubmed.ncbi.nlm.nih.gov/12629218/) | Human breast-cancer xenotransplantation. Marker-selected cells generated and serially propagated heterogeneous tumours. | Assay selection and patient context bound the inference. |
| 2008 | [Efficient tumour formation by single human melanoma cells.](https://pubmed.ncbi.nlm.nih.gov/19052619/) | Permissive melanoma transplantation. Changing host/assay conditions revealed frequent tumour-forming capacity, including single-cell transplants. | Tumour formation in a recipient does not identify an endogenous fixed hierarchy. |
| 2012 | [A restricted cell population propagates glioblastoma growth after chemotherapy.](https://pubmed.ncbi.nlm.nih.gov/22854781/) | Mouse glioma tracing and ablation. A relatively quiescent population sustained regrowth after chemotherapy; ablation restricted growth. | Dependency applies to the tested model and treatment setting. |
| 2012 | [Lineage tracing reveals Lgr5+ stem cell activity in mouse intestinal adenomas.](https://pubmed.ncbi.nlm.nih.gov/22855427/) | Mouse adenoma lineage tracing. Lgr5-positive cells self-renewed and generated other adenoma cells. | Adenoma lineage behaviour does not generalize automatically to invasive carcinoma. |
| 2017 | [Visualization and targeting of LGR5+ human colon cancer stem cells.](https://pubmed.ncbi.nlm.nih.gov/28355176/) | Human colorectal organoid tracing/ablation. Differentiated cells reverted and contributed to regrowth after LGR5-positive depletion. | Organoid/xenograft plasticity is distinct from patient relapse under therapeutic targeting. |
| 2017 | [A distinct role for Lgr5+ stem cells in primary and metastatic colon cancer.](https://pubmed.ncbi.nlm.nih.gov/28358093/) | Mouse colorectal ablation. Lgr5-negative cells maintained primary tumours and replenished the Lgr5-positive pool. | Primary and metastatic dependencies differed. |
| 2020 | [Plasticity of Lgr5-Negative Cancer Cells Drives Metastasis in Colorectal Cancer.](https://pubmed.ncbi.nlm.nih.gov/32169167/) | Colorectal dissemination models. Lgr5-negative disseminated cells acquired stem-like capacity during metastatic outgrowth. | Establishment and outgrowth are different causal stages. |
| 2022 | [Metastatic recurrence in colorectal cancer arises from residual EMP1+ cells.](https://pubmed.ncbi.nlm.nih.gov/36352230/) | Post-resection colorectal mouse model. Residual EMP1-high cells generated recurrence; their ablation prevented relapse. | A specific residual state and model do not establish a universal marker-defined apex. |
| 2026 | [Critical role for a high-plasticity cell state in lung cancer.](https://pubmed.ncbi.nlm.nih.gov/41565826/) | Lung-cancer state tracing and ablation. A high-plasticity state contributed to progression and treatment resistance. | State targeting and context-specific necessity do not prove irreplaceability across tumours. |
| 2026 | [ZFP36L2 orchestrates stress-adaptive plasticity in regeneration and cancer.](https://pubmed.ncbi.nlm.nih.gov/42557330/) | Regeneration and colorectal perturbation. ZFP36L2 regulated stress-adaptive dedifferentiation and lineage plasticity. | Loss of canonical stem-state entry can permit alternative malignant states. |

## Research gaps

### G1: How rare is tumour-sustaining capacity in the native tumour?

Evidence anchors: [P9212098](https://pubmed.ncbi.nlm.nih.gov/9212098/), [P12629218](https://pubmed.ncbi.nlm.nih.gov/12629218/), [P19052619](https://pubmed.ncbi.nlm.nih.gov/19052619/), [P22855427](https://pubmed.ncbi.nlm.nih.gov/22855427/).

Competing explanation: Host permissiveness and sorting may create apparent rarity.

Discriminating test and controls: Pair transplantation with endogenous lineage tracing; vary recipient immune status, matrix and cell viability while fixing sampling and follow-up.

### G2: Can other states replace the depleted compartment?

Evidence anchors: [P28358093](https://pubmed.ncbi.nlm.nih.gov/28358093/), [P28355176](https://pubmed.ncbi.nlm.nih.gov/28355176/), [P32169167](https://pubmed.ncbi.nlm.nih.gov/32169167/), [P42557330](https://pubmed.ncbi.nlm.nih.gov/42557330/).

Competing explanation: Apparent escape may reflect incomplete ablation or true state conversion.

Discriminating test and controls: Permanent pre-ablation lineage labels and ablation-efficiency measurement; distinguish residual target cells from converted progeny over long follow-up.

### G3: Which cell state maintains post-treatment residual disease?

Evidence anchors: [P22854781](https://pubmed.ncbi.nlm.nih.gov/22854781/), [P36352230](https://pubmed.ncbi.nlm.nih.gov/36352230/), [P41565826](https://pubmed.ncbi.nlm.nih.gov/41565826/).

Competing explanation: A relapse-specific state may differ from the primary-tumour initiating population.

Discriminating test and controls: Track residual states after standard therapy or surgery; randomize state-specific targeting and assess relapse, not transplantation alone.

### G4: Does targeting a state improve human outcomes without bypass?

Evidence anchors: [P28355176](https://pubmed.ncbi.nlm.nih.gov/28355176/), [P36352230](https://pubmed.ncbi.nlm.nih.gov/36352230/), [P41565826](https://pubmed.ncbi.nlm.nih.gov/41565826/).

Competing explanation: Off-target killing or niche alteration may produce benefit while other states replenish function.

Discriminating test and controls: Biomarker-stratified human trials with paired biopsies, target depletion, escape-state tracking, hard outcomes and combination controls.

## Methods and access

Case-specific Consensus records assisted gap discovery, chronology and targeted paper questions. Shared template wording about an amyloid-specific Deep follow-up is not evidence of a Deep run for this topic; the dated source records establish the actual use and access limits. Primary identifiers, selected abstract passages, correction notices and available primary-body passages were cross-checked. Generated absence cells, duplicate milestones and unsupported access claims were rejected.

This focused addendum does not establish 50–70 complete primary Methods/Results examinations per review. Baseline reading receipts and scores retain their original scope.

Checked timeline sources: 11; selected full-text checks: 1; abstract-excerpt checks: 10; metadata-only historical anchors: 0. Complete papers examined in this update: 0.

Historical scorecards declare schema 5.4. This enrichment uses HSEF v5.3 causal distinctions without retrospectively relabelling or rescoring those files.

Targeted paper-check scope: Single-cell figure passage and Methods Summary P25: single cells were mixed with Matrigel and transplanted into permissive hosts; host/assay conditions are explicit.

Editorial correction/limit: Consensus often cited later reviews for original experimental claims. Those citations were not accepted as primary verification.