SAA1 polymorphisms are associated with variation in antiangiogenic and tumor-suppressive activities in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a cancer that occurs in high frequency in Southern China. A previous functional complementation approach and the subsequent cDNA microarray analysis have identified that serum amyloid A1 (SAA1) is an NPC candidate tumor suppressor gene. SAA1 belongs to a family of acute-phase proteins that are encoded by five polymorphic coding alleles. The SAA1 genotyping results showed that only three SAA1 isoforms (SAA1.1, 1.3 and 1.5) were observed in both Hong Kong NPC patients and healthy individuals. This study aims to determine the functional role of SAA1 polymorphisms in tumor progression and to investigate the relationship between SAA1 polymorphisms and NPC risk. Indeed, we have shown that restoration of SAA1.1 and 1.3 in the SAA1-deficient NPC cell lines could suppress tumor formation and angiogenesis in vitro and in vivo. The secreted SAA1.1 and SAA1.3 proteins can block cell adhesion and induce apoptosis in the vascular endothelial cells. In contrast, the SAA1.5 cannot induce apoptosis or inhibit angiogenesis because of its weaker binding affinity to αVβ3 integrin. This can explain why SAA1.5 has no tumor-suppressive effects. Furthermore, the NPC tumors with this particular SAA1.5/1.5 genotype showed higher levels of SAA1 gene expression, and SAA1.1 and 1.3 alleles were preferentially inactivated in tumor tissues that were examined. These findings further strengthen the conclusion for the defective function of SAA1.5 in suppression of tumor formation and angiogenesis. Interestingly, the frequency of the SAA1.5/1.5 genotype in NPC patients was ~2-fold higher than in the healthy individuals (P=0.00128, odds ratio=2.28), which indicates that this SAA1 genotype is significantly associated with a higher NPC risk. Collectively, this homozygous SAA1.5/1.5 genotype appears to be a recessive susceptibility gene, which has lost the antiangiogenic function, whereas SAA1.1 and SAA1.3 are the dominant alleles of the tumor suppressor phenotype.

Analyzing white blood cell subpopulation for quick and simple predictors for autologous stem cell collection

7101

Background: For patients undergoing peripheral stem cell harvesting, the current standard predictor for successful harvest is the peripheral blood (PB)CD34 count, which may have a slow turn-around time. Daily monitoring of CD34 count may not be cost-effective. This study aims to identify simple hematological parameters that can be used to predict for a single day CD 34+ stem cell yield of at least 1 x 10(6)/kg. Methods: 57 patients with lymphoproliferative malignancies who underwent autologous stem cell (ASC) harvesting were studied following DHAP, ICE or ESHAP chemotherapy. Eight main parameters were investigated to predict for a single day CD34 stem cell yield above 1x10(6)/kg: PB CD34+ cells, absolute monocyte count (AMC), AMC ratio, total white count (WBC), absolute lymphocyte count (ALC), ALC ratio, immature granulocyte count (IMC), IMC ratio and non-neutrophil cells (NNC). NNC was calculated by subtracting absolute neutrophil count from the total white count. The ratios were calculated by dividing the respective values on the first day of harvest with the values on the day before mobilizing chemotherapy started. Results: Linear regression showed a strong correlation between stem cell yield and CD34+ cells (R2=0.79, p<0.001), IMC ratio (R2=0.51, p<0.001) and AMC ratio (R2= 0.46, P<0.001). WBC and AMC showed a wide dispersion of results and were not reliable predictors of CD34 yield. On multivariate analysis, an IMC > 1 (p=0.03) and AMC ratio > 1 (p=0.002), ALC ratio > 1 (p=0.03) were independently predictive of a single day CD34 stem cell yield exceeding 1x10(6)/kgConclusions: Incorporating simple, routine hematolgic indices such as ALC and AMC ratio into a simple formula can be used to predict for ASC collection in addition to CD34+ count. This may be particularly useful when the turn-around-time to attain enumeration of CD34+ cells is slow or delayed on the same day of collection.

No significant financial relationships to disclose.