Peripheral blood stem cells (PBSCs) are increasingly used as the source of hematopoietic stem cells, but there are large variations in harvest outcome between individuals mobilized by granulocyte colony-stimulating factor (G-CSF). We examined the effects of donor characteristics and procedure factors on the day 1 CD34+ cell yield in 373 unrelated healthy donors. G-CSF was administered subcutaneously at a planned dose of 8.3 to 11 microg/kg daily for 5 days, followed by harvest started on day 5 of G-CSF treatment. Of the 373 donors, 159 (42.6%) had the radial artery as the inlet access for harvest. Poor day 1 cell yield was defined as <10x10(6) CD34+ cells/L of processed blood for the first apheresis; 62 donors (16.6%) did not attain this threshold. The male donors had significantly higher yields at harvest compared with the female donors. The female donors had higher CD34+ cell yields if the circulation access was through an artery than if is was through a vein. In a multiple regression analysis, donor age, sex, body mass index (BMI), preharvest white blood cell and circulating immature cell counts, access type, and flow rate correlated with day 1 yield. Female sex, older age, venous access, and a higher flow rate were significantly associated with greater risk for a day 1 poor yield of CD34+ cells (odds ratio=3.0074, 1.045, 4.3362, and 1.1131, respectively). A higher BMI may decrease the risk (odds ratio=0.8472). In donors at higher risk for poor CD34+ cell yield, strategies for increasing CD34+ cells must be considered.

Human pituitary tumour-transforming gene 1 (hPTTG1) is an oncogenic transcription factor that is overexpressed in many tumour types, especially tumours with metastatic abilities. However, how hPTTG1 overexpression drives metastasis is not yet clear. As a transcription factor, hPTTG1 may promote metastasis by activating target genes that are involved in the metastatic process. Here, we showed that Rho guanine nucleotide exchange factor-H1 (GEF-H1) was transcriptionally activated by hPTTG1, thereby promoting breast cancer metastasis. Luciferase reporter analyses and chromatin immunoprecipitation (ChIP) assays showed that hPTTG1 directly bound and activated the GEF-H1 gene promoter. In this study, RNA interference-mediated knockdown of hPTTG1 in highly metastatic breast tumour cells decreased GEF-H1 expression and RhoA activation, thereby reducing cell motility and invasion, and interfering with cytoskeletal remodelling in vitro, and impairing the tumour metastasis in vivo. The restoration of GEF-H1 expression in hPTTG1-knockdown cells rescued the hPTTG1-knockdown effects on cytoskeletal changes in vitro and tumour metastasis in vivo. Conversely, ectopic expression of hPTTG1 in non-metastatic breast tumour cells induced cytoskeletal rearrangements, and allowed these cells to metastasise in a mouse model by orthotopic implantation. In human tumour samples, hPTTG1 expression was also correlated to GEF-H1 expression in aggressive breast carcinoma. Altogether, these findings definitively establish a role for hPTTG1 in activating the GEF-H1/RhoA pathway as a newly identified mechanism in breast cancer metastasis.

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