Differing effects of microtubule depolymerizing and stabilizing chemotherapeutic agents on t-SNARE–mediated apical targeting of prostate-specific membrane antigen

Colchicine Significantly Reduces Incident Cancer in Gout Male Patients: A 12-Year Cohort Study

Patients with gout are more likely to develop most cancers than subjects without gout. Colchicine has been used for the treatment and prevention of gouty arthritis and has been reported to have an anticancer effect in vitro. However, to date no study has evaluated the relationship between colchicine use and incident cancers in patients with gout. This study enrolled male patients with gout identified in Taiwan's National Health Insurance Database for the years 1998 to 2011. Each gout patient was matched with 4 male controls by age and by month and year of first diagnosis, and was followed up until 2011. The study excluded those who were diagnosed with diabetes or any type of cancer within the year following enrollment. We calculated hazard ratio (HR), aged-adjusted standardized incidence ratio, and incidence of 1000 person-years analyses to evaluate cancer risk. A total of 24,050 male patients with gout and 76,129 male nongout controls were included. Patients with gout had a higher rate of incident all-cause cancers than controls (6.68% vs 6.43%, P = 0.006). A total of 13,679 patients with gout were defined as having been ever-users of colchicine and 10,371 patients with gout were defined as being never-users of colchicine. Ever-users of colchicine had a significantly lower HR of incident all-cause cancers than never-users of colchicine after adjustment for age (HR = 0.85, 95% CI = 0.77-0.94; P = 0.001). In conclusion, colchicine use was associated with a decreased risk of incident all-cause cancers in male Taiwanese patients with gout.

Pairwise comparison of 89Zr- and 124I-labeled cG250 based on positron emission tomography imaging and nonlinear immunokinetic modeling: in vivo carbonic anhydrase IX receptor binding and internalization in mouse xenografts of clear-cell renal cell carcinoma

PURPOSE

The PET tracer, (124)I-cG250, directed against carbonic anhydrase IX (CAIX) shows promise for presurgical diagnosis of clear-cell renal cell carcinoma (ccRCC) (Divgi et al. in Lancet Oncol 8:304-310, 2007; Divgi et al. in J Clin Oncol 31:187-194, 2013). The radiometal (89)Zr, however, may offer advantages as a surrogate PET nuclide over (124)I in terms of greater tumor uptake and retention (Rice et al. in Semin Nucl Med 41:265-282, 2011). We have developed a nonlinear immunokinetic model to facilitate a quantitative comparison of absolute uptake and antibody turnover between (124)I-cG250 and (89)Zr-cG250 using a human ccRCC xenograft tumor model in mice. We believe that this unique model better relates quantitative imaging data to the salient biological features of tumor antibody-antigen binding and turnover.

METHODS

We conducted experiments with (89)Zr-cG250 and (124)I-cG250 using a human ccRCC cell line (SK-RC-38) to characterize the binding affinity and internalization kinetics of the two tracers in vitro. Serial PET imaging was performed in mice bearing subcutaneous ccRCC tumors to simultaneously detect and quantify time-dependent tumor uptake in vivo. Using the known specific activities of the two tracers, the equilibrium rates of antibody internalization and turnover in the tumors were derived from the PET images using nonlinear compartmental modeling.

RESULTS

The two tracers demonstrated virtually identical tumor cell binding and internalization but showed markedly different retentions in vitro. Superior PET images were obtained using (89)Zr-cG250, owing to the more prolonged trapping of the radiolabel in the tumor and simultaneous washout from normal tissues. Estimates of cG250/CAIX complex turnover were 1.35 - 5.51 × 10(12) molecules per hour per gram of tumor (20 % of receptors internalized per hour), and the ratio of (124)I/(89)Zr atoms released per unit time by tumor was 17.5.

CONCLUSION

Pairwise evaluation of (89)Zr-cG250 and (124)I-cG250 provided the basis for a nonlinear immunokinetic model which yielded quantitative information about the binding and internalization of radioantibody bound to CAIX on tumor cells in vivo. (89)Zr-cG250 is likely to provide high-quality PET images and may be a useful tool to quantify CAIX/cG250 receptor turnover and cG250-accessible antigen density noninvasively in humans.

Docetaxel down-regulates the expression of androgen receptor and prostate-specific antigen but not prostate-specific membrane antigen in prostate cancer cell lines: implications for PSA surrogacy

BACKGROUND

Docetaxel (DOC) has potent anti-tumor efficacy as a result of promoting microtubule assembly and microtubule bundling thereby impairing mitosis. Knowing that some anti-microtubule agents affect the polarity of prostate-specific membrane antigen (PSMA) expression and that androgen ablation can up-regulate PSMA expression, we sought to determine any effect of DOC on PSMA expression in prostate cancer (PC) cell lines as a prelude to a clinical effort. As controls, we also looked at the expression of androgen receptor (AR) and prostate-specific antigen (PSA).

METHODS

The effect of DOC on cell viability and PSMA, AR, and PSA expression was examined by flow cytometry and immunoblotting using LNCaP, CWR22Rv1, and MDA-PCa-2b cells. The effect of DOC on PSA levels of LNCaP and MDA-PCa-2b cells was also measured in conditioned media. The effect of DOC was also studied using LNCaP and MDA-PCa-2b cells that were transfected to over-express AR.

RESULTS

PSMA levels were not affected by DOC treatment. Unexpectedly, we found DOC significantly down-regulated both AR and PSA in a dose-dependent manner in the cell lines studied. Over-expression of AR partially abrogated the cytotoxic effects of DOC.

CONCLUSIONS

While DOC did not affect PSMA expression, it was unexpectedly found to down-regulate AR and PSA. DOC-induced down-regulation of AR might be one of the anti-tumor mechanisms active in PC. Down-regulation of PSA may account for the significantly higher PSA response rates (45-50%) relative to measurable response rates (8-17%) reported in DOC PC trials and have implications for PSA surrogacy observations derived from DOC trials.