Cancer stem cells (CSCs) are a promising target for treating cancer, yet how CSC plasticity is maintained in vivo is unclear and is difficult to study in vitro. Here we establish a sustainable primary culture of Oct3/4(+)/Nanog(+) lung CSCs fed with CD90(+) cancer-associated fibroblasts (CAFs) to further advance our knowledge of preserving stem cells in the tumour microenvironment. Using transcriptomics we identify the paracrine network by which CAFs enrich CSCs through de-differentiation and reacquisition of stem cell-like properties. Specifically, we find that IGF1R signalling activation in cancer cells in the presence of CAFs expressing IGF-II can induce Nanog expression and promote stemness. Moreover, this paracrine signalling predicts overall and relapse-free survival in stage I non-small cell lung cancer (NSCLC) patients. IGF-II/IGF1R signalling blockade inhibits Nanog expression and attenuates cancer stem cell features. Our data demonstrate that CAFs constitute a supporting niche for cancer stemness, and targeting this paracrine signalling may present a new therapeutic strategy for NSCLC.

Mesenchymal stem/stromal cells (MSCs) are a promising resource for cell-based therapy because of their high immunomodulation ability, tropism towards inflamed and injured tissues, and their easy access and isolation. Currently, there are more than 1200 registered MSC clinical trials globally. However, a lack of standardized methods to characterize cell safety, efficacy, and biodistribution dramatically hinders the progress of MSC utility in clinical practice. In this review, we summarize the current state of MSC-based cell therapy, focusing on the systemic safety and biodistribution of MSCs. MSC-associated risks of tumor initiation and promotion and the underlying mechanisms of these risks are discussed. In addition, MSC biodistribution methodology and the pharmacokinetics and pharmacodynamics of cell therapies are addressed. Better understanding of the systemic safety and biodistribution of MSCs will facilitate future clinical applications of precision medicine using stem cells.

In this study, we report a serum-free culture system for primary neonatal pulmonary cells that can support the growth of octamer-binding transcription factor 4 ⁺ (Oct-4 ⁺ ) epithelial colonies with a surrounding mesenchymal stroma. In addition to Oct-4, these cells also express other stem cell markers such as stage-specific embryonic antigen 1 (SSEA-1), stem cell antigen 1 (Sca-1), and Clara cell secretion protein (CCSP) but not c-Kit, CD34, and p63, indicating that they represent a subpopulation of Clara cells that have been implicated as lung stem/progenitor cells in lung injury models. These colony cells can be kept for weeks in primary cultures and undergo terminal differentiation to alveolar type-2- and type-1-like pneumocytes sequentially when removed from the stroma. In addition, we have demonstrated the presence of Oct-4 ⁺ long-term BrdU label-retaining cells at the bronchoalveolar junction of neonatal lung, providing a link between the Oct-4 ⁺ cells in vivo and in vitro and strengthening their identity as putative neonatal lung stem/progenitor cells. Lastly, these Oct-4 ⁺ epithelial colony cells, which also express angiotensin-converting enzyme 2, are the target cells for severe acute respiratory syndrome coronavirus infection in primary cultures and support active virus replication leading to their own destruction. These observations imply the possible involvement of lung stem/progenitor cells, in addition to pneumocytes, in severe acute respiratory syndrome coronavirus infection, accounting for the continued deterioration of lung tissues and apparent loss of capacity for lung repair.

The type V TGF‐β receptor (TβR‐V)/IGFBP‐3 receptor mediates the IGF‐independent growth inhibition induced by IGFBP‐3. It also mediates the growth inhibitory response to TGF‐β ₁ in concert with other TGF‐β receptor types, and its loss may contribute to the malignant phenotype of human carcinoma cells. Here we demonstrate that TβR‐V is identical to LRP‐1/α ₂ M receptor as shown by MALDI‐TOF analysis of tryptic peptides of TβR‐V purified from bovine liver. In addition, ¹²⁵ I‐IGFBP‐3 affinity‐labeled TβR‐V in Mv1Lu cells is immunoprecipitated by antibodies to LRP‐1 and TβR‐V. RAP, an LRP‐1 antagonist, inhibits binding of ¹²⁵ I‐TGF‐β ₁ and ¹²⁵ I‐IGFBP‐3 to Tβ R‐V and diminishes IGFBP‐3‐induced growth inhibition in Mv1Lu cells. Absent or low levels of LRP‐1, as with TβR‐V, have been linked to the malignant phenotype of carcinoma cells. Mutagenized Mv1Lu cells selected for reduced expression of LRP‐1 have an attenuated growth inhibitory response to TGF‐β ₁ and IGFBP‐3. LRP‐1‐deficient mouse embryonic fibroblasts lack a growth inhibitory response to TGF‐β ₁ and IGFBP‐3. On the other hand, stable transfection of H1299 human lung carcinoma cells with LRP‐1 cDNA restores the growth inhibitory response. These results suggest that the LRP‐1/TβR‐V/IGFBP‐3 receptor is required for the growth inhibitory response to IGFBP‐3 and TGF‐β ₁ .—Huang, S. S., Ling, T.‐Y., Tseng, W.‐F., Huang, Y.‐H., Tang, F.‐M., Leal, S. M., Huang, J. S. Cellular growth inhibition by IGFBP‐3 and TGF‐β1 requires LRP‐1. FASEB J. 17, 2068–2081 (2003)