Preclinical and Clinical Estimates of the Basal Apoptotic Rate of a Cancer Predict the Amount of Apoptosis Induced by Subsequent Proapoptotic Stimuli

Abstract

Purpose: We hypothesized that the basal apoptotic rate (BAR) of a cancer would predict sensitivity to subsequent proapoptotic stimuli. To explore this, preclinical and clinical BAR assays were developed measuring cumulative apoptotic events through ELISAs for soluble caspase-cleaved cytokeratin 18 (M30) normalized to either cell number increase or total tumor volume, respectively.Experimental Design: The BARs of A549, HCC44, and SW1573 non-small cell lung carcinoma cell lines were measured following different pro/antiapoptotic manipulations. In isogenic wild-type and stable knockdown (KD) series, pretreatment BARs were correlated with response to proapoptotic stimuli and compared with established apoptosis assays. Pretreatment and posttreatment serum was available from stereotactic body radiation therapy patients.Results: Caspase inhibition and p53 KDs reduced the BAR, whereas serum deprivation, XIAP, or Bcl2 KDs increased the BAR. The nontreated BAR rank ordering of the XIAP series recapitulated that with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and caspase-3/7 activity assays, and predicted each line's sensitivity to TRAIL or irradiation. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, however, underestimated basal apoptosis during increased apoptotic stress, and caspase-3/7 activity detected minimal death in the media. P53 KDs with lower nontreated BARs were less sensitive to TRAIL and cisplatinum than wild-type. Stereotactic body radiation therapy increased serum M30 values, and the pretreatment clinical BAR strongly correlated with fold change in M30 on treatment (r = 0.93).Conclusions: M30-based BAR assays reflect apoptosis accurately and are more amenable to clinical application than existing apoptosis assays. The pretreatment BAR correlates with cell and/or tumor sensitivity to extrinsic and intrinsic apoptotic pathway stimulation. Prospective clinical exploration is warranted.

On the TRAIL to successful cancer therapy? Predicting and counteracting resistance against TRAIL-based therapeutics

“…In a study by Zhang et al, the basal apoptotic rate (BAR) of tumors was measured by the cleavage of the apoptosis substrate keratin 18 before and after treatment with TRAIL. The results were encouraging, showing that an initial high BAR was more likely to lead to a total BAR increase after treatment (110). …”

The Chinese Herb Isolate Isorhapontigenin Induces Apoptosis in Human Cancer Cells by Down-regulating Overexpression of Antiapoptotic Protein XIAP

“…There is growing evidence showing the correlation between XIAP overexpression and malignant cancer aggression (4), drug resistance (26), and poor clinical prognosis in many malignancies (27). Poorly differentiated carcinomas also display significantly higher levels of XIAP expression than well differentiated carcinomas (28).…”

Irradiation Promotes an M2 Macrophage Phenotype in Tumor Hypoxia

“…The recurrent tumors are not only less responsive to salvage RT or chemotherapy, but also have a higher risk of metastasis (Vicini et al, 2003). Although the effects of hypo-perfusion and low oxygen contents on tumor cells are often blamed for poor treatment response, distinct tumor microenvironments within hypoxic regions such as where there are more acidic or contain high numbers or distinct populations of macrophages, also play significant roles in tumor resistance to therapy (Jiang et al, 2010; Zhang et al, 2010; Denardo et al, 2011). Several new treatment protocols to target the tumor microenvironments have been suggested, such as pH responsive drug delivery (Chiu et al, 1999; Benoit et al, 2010) and macrophage-targeted (Ahn et al, 2010; Jiang et al, 2010) or -assisted (Alizadeh et al, 2010; Muthana et al, 2011) cancer therapy.…”

“…They were originally thought of as one host defense mechanism against the developing cancer. However, evidence has accumulated indicating that TAMs may assist tumors to survive hazardous environments in various ways (Nishie et al, 1999; Bingle et al, 2002; Murdoch and Lewis, 2005; Lewis and Pollard, 2006; Li et al, 2007; Ahn and Brown, 2008; Qian and Pollard, 2010; Chen et al, 2011) and even promote tumor resistance to chemotherapy (Zhang et al, 2010; Denardo et al, 2011). Two distinct TAM phenotypes, M1 or M2, have been described with the abilities to inhibit or promote tumor growth, respectively.…”