Racial disparities in cancer-associated thrombosis.

Race and ethnicity are associated with risk of venous thromboembolism in population-based studies. Blacks/African Americans have a higher incidence, whereas Asians/Pacific Islanders and Hispanics have a lower incidence of venous thromboembolism compared with non-Hispanic Whites. The impact of race/ethnicity on the incidence of cancer-associated thrombosis (CAT), a common complication in patients with malignancy, has not been well defined. Using the California Cancer Registry linked to the California Patient Discharge Dataset and Emergency Department Utilization database, we studied a large, diverse cohort of patients (n = 942 109) from 2005 to 2017 with the 13 most common, first primary malignancies to determine the association between race/ethnicity and incidence of incident and recurrent CAT. Multivariable Cox proportional hazards regression models were performed to determine the effect of race/ethnicity on the risk of overall CAT, specific CAT by location, and recurrent CAT. Blacks/African Americans had a higher incidence of CAT for all tumor types except myeloma, whereas Asians/Pacific Islanders had a consistently lower incidence of CAT compared with non-Hispanic Whites, after adjusting for potential confounders. The main driver for the racial/ethnic differences was incidence of pulmonary embolism. We speculate the association of race/ethnicity with incidence of CAT may be partially because of underlying thrombotic predisposition that varies by ancestry, but we also must consider the impact of social determinants of health on our results.

ER stress-mediated autophagy promotes Myc-dependent transformation and tumor growth.

The proto-oncogene c-Myc paradoxically activates both proliferation and apoptosis. In the pathogenic state, c-Myc-induced apoptosis is bypassed via a critical, yet poorly understood escape mechanism that promotes cellular transformation and tumorigenesis. The accumulation of unfolded proteins in the ER initiates a cellular stress program termed the unfolded protein response (UPR) to support cell survival. Analysis of spontaneous mouse and human lymphomas demonstrated significantly higher levels of UPR activation compared with normal tissues. Using multiple genetic models, we demonstrated that c-Myc and N-Myc activated the PERK/eIF2α/ATF4 arm of the UPR, leading to increased cell survival via the induction of cytoprotective autophagy. Inhibition of PERK significantly reduced Myc-induced autophagy, colony formation, and tumor formation. Moreover, pharmacologic or genetic inhibition of autophagy resulted in increased Myc-dependent apoptosis. Mechanistically, we demonstrated an important link between Myc-dependent increases in protein synthesis and UPR activation. Specifically, by employing a mouse minute (L24+/-) mutant, which resulted in wild-type levels of protein synthesis and attenuation of Myc-induced lymphomagenesis, we showed that Myc-induced UPR activation was reversed. Our findings establish a role for UPR as an enhancer of c-Myc-induced transformation and suggest that UPR inhibition may be particularly effective against malignancies characterized by c-Myc overexpression.

Thioredoxin reductase-1 mediates curcumin-induced radiosensitization of squamous carcinoma cells.

Curcumin, a plant polyphenol, is a widely studied chemopreventive agent with demonstrated antitumor activities in preclinical studies and low toxicity profiles in multiple clinical trials against human malignancies. We previously showed that curcumin radiosensitizes cervical tumor cells without increasing the cytotoxic effects of radiation on normal human fibroblasts. Here we report that an inhibitory activity of curcumin on the antioxidant enzyme thioredoxin reductase-1 (TxnRd1) is required for curcumin-mediated radiosensitization of squamous carcinoma cells. Stable knockdown of TxnRd1 in both HeLa and FaDu cells nearly abolished curcumin-mediated radiosensitization. TxnRd1 knockdown cells showed decreased radiation-induced reactive oxygen species and sustained extracellular signal-regulated kinase 1/2 activation, which we previously showed was required for curcumin-mediated radiosensitization. Conversely, overexpressing catalytically active TxnRd1 in HEK293 cells, with low basal levels of TxnRd1, increased their sensitivity to curcumin alone and to the combination of curcumin and ionizing radiation. These results show the critical role of TxnRd1 in curcumin-mediated radiosensitization and suggest that TxnRd1 levels in tumors could have clinical value as a predictor of response to curcumin and radiotherapy.