D. Gwyn Bebb

Enhanced cytotoxicity of PARP inhibition in mantle cell lymphoma harbouring mutations in both ATM and p53

Poly‐ADP ribose polymerase (PARP) inhibitors have shown promise in the treatment of human malignancies characterized by deficiencies in the DNA damage repair proteins BRCA1 and BRCA2 and preclinical studies have demonstrated the potential effectiveness of PARP inhibitors in targeting ataxia‐telangiectasia mutated (ATM)‐deficient tumours. Here, we show that mantle cell lymphoma (MCL) cells deficient in both ATM and p53 are more sensitive to the PARP inhibitor olaparib than cells lacking ATM function alone. In ATM‐deficient MCL cells, olaparib induced DNA‐PK‐dependent phosphorylation and stabilization of p53 as well as expression of p53‐responsive cell cycle checkpoint regulators, and inhibition of DNA‐PK reduced the toxicity of olaparib in ATM‐deficient MCL cells. Thus, both DNA‐PK and p53 regulate the response of ATM‐deficient MCL cells to olaparib. In addition, small molecule inhibition of both ATM and PARP was cytotoxic in normal human fibroblasts with disruption of p53, implying that the combination of ATM and PARP inhibitors may have utility in targeting p53‐deficient malignancies.

Low ATM protein expression and depletion of p53 correlates with olaparib sensitivity in gastric cancer cell lines

Small-molecule inhibitors of poly (ADP-ribose) polymerase (PARP) have shown considerable promise in the treatment of homologous recombination (HR)-defective tumors, such as BRCA1- and BRCA2-deficient breast and ovarian cancers. We previously reported that mantle cell lymphoma cells with deficiency in ataxia telangiectasia mutated (ATM) are sensitive to PARP-1 inhibitors in vitro and in vivo. Here, we report that PARP inhibitors can potentially target ATM deficiency arising in a solid malignancy. We show that ATM protein expression varies between gastric cancer cell lines, with NUGC4 having significantly reduced protein levels. Significant correlation was found between ATM protein expression and sensitivity to the PARP inhibitor olaparib, with NUGC4 being the most sensitive. Moreover, reducing ATM kinase activity using a small-molecule inhibitor (KU55933) or shRNA-mediated depletion of ATM protein enhanced olaparib sensitivity in gastric cancer cell lines with depletion or inactivation of p53. Our results demonstrate that ATM is a potential predictive biomarker for PARP-1 inhibitor activity in gastric cancer harboring disruption of p53, and that combined inhibition of ATM and PARP-1 is a rational strategy for expanding the utility of PARP-1 inhibitors to gastric cancer with p53 disruption.

CXCR4 Overexpression Is Associated with Poor Outcome in Females Diagnosed with Stage IV Non-small Cell Lung Cancer

Background: It has been proposed that the chemokine receptor, CXCR4, and its ligand, stromal cell-derived factor-1 (SDF-1), play a critical role in organ-specific tumor metastasis. High CXCR4 expression in resected non-small cell lung cancer (NSCLC) tumors is associated with poorer outcome; however, its effect on patient outcome in advanced NSCLC has not been explored. Methods: After institutional ethical approval was obtained, demographic details, clinical variables, and outcome data were collected on consecutive NSCLC patients diagnosed at the Tom Baker Cancer Centre from 2003 to 2006 (Glans-Look Lung Cancer Database). Formalin-fixed paraffin-embedded diagnostic biopsies from stage IV patients were obtained and tissue microarrays generated. CXCR4 expression within NSCLC cells was analyzed by quantitative fluorescent immunohistochemistry using the HistoRx PM-2000 platform and then correlated with clinical outcome. Results: Of 832 patients, 170 had samples suitable for tissue microarray generation and analysis. Automated immunohistochemistry for CXCR4 was successfully completed on all 170 patients. High expressors had a significantly poorer median overall survival of 2.7 months versus 5.6 months for the low expressors (p = 0.0468). This difference is driven by high-expressing females who have a median overall survival of 1.6 months versus 6.4 months for the low expressors (p = 0.006). Conclusions: CXCR4 is expressed in the majority of NSCLC tumors, and overexpression is associated with significantly poorer survival in stage IV NSCLC patients. Interestingly, this poor outcome is disproportionately represented in the female population. Our results suggest a gender-dependent difference in clinical outcome based on CXCR4 overexpression in stage IV NSCLC.

Physical activity and diet behaviour in colorectal cancer patients receiving chemotherapy: associations with quality of life

BackgroundThe relationship between colorectal cancer (CRC) risk and physical activity and dietary habits has been well-established, but less is known about the relationship between these behaviours and quality of life (QOL) post-diagnosis. Moreover, it is unknown whether this relationship is consistent across cancer stage or treatment setting. Thus, the purpose of this study was to assess current diet and physical activity behaviour in CRC survivors receiving systemic chemotherapy, and to examine potential associations between these behaviours and quality of life. A secondary purpose was to examine the association between social support, diet, and physical activity behaviour in this population.MethodsUsing a cross-sectional survey, 67 CRC survivors currently receiving chemotherapy in Calgary, Alberta completed the survey package. Measures included demographic and medical data, physical activity levels, diet behaviour, QOL, and social support.ResultsIn a largely metastatic sample (63%), approximately half were meeting national dietary guidelines (58%), less were meeting national physical activity guidelines (26%), and a small number were meeting both (17%). However, only 12.3% (n = 8) reported completely sedentary behaviour, and 7 of these 8 participants were receiving metastatic treatment. Neither behaviour was significantly associated with QOL or perceived social support. Furthermore, there were no significant QOL differences between those treated with palliative intent or adjuvant therapy. Important group differences emerged between those meeting and not meeting the guidelines, and associations between QOL, age, BMI, and provisions of social support.ConclusionThese findings provide insight into lifestyle behaviours of CRC survivors currently receiving systemic chemotherapy, and the differences in perceived QOL as affected by severity of disease and treatment setting. Prospective studies in a larger sample of CRC survivors on chemotherapy are needed to confirm lifestyle behaviour patterns and identify factors related to QOL that are unique to this population, especially during metastatic treatment.

ATM-Deficient Colorectal Cancer Cells Are Sensitive to the PARP Inhibitor Olaparib

The ataxia telangiectasia mutated (ATM) protein kinase plays a central role in the cellular response to DNA damage. Loss or inactivation of both copies of the ATM gene (ATM) leads to ataxia telangiectasia, a devastating childhood condition characterized by neurodegeneration, immune deficiencies, and cancer predisposition. ATM is also absent in approximately 40% of mantle cell lymphomas (MCLs), and we previously showed that MCL cell lines with loss of ATM are sensitive to poly-ADP ribose polymerase (PARP) inhibitors. Next-generation sequencing of patient tumors has revealed that ATM is altered in many human cancers including colorectal, lung, prostate, and breast. Here, we show that the colorectal cancer cell line SK-CO-1 lacks detectable ATM protein expression and is sensitive to the PARP inhibitor olaparib. Similarly, HCT116 colorectal cancer cells with shRNA depletion of ATM are sensitive to olaparib, and depletion of p53 enhances this sensitivity. Moreover, HCT116 cells are sensitive to olaparib in combination with the ATM inhibitor KU55933, and sensitivity is enhanced by deletion of p53. Together our studies suggest that PARP inhibitors may have potential for treating colorectal cancer with ATM dysfunction and/or colorectal cancer with mutation of p53 when combined with an ATM kinase inhibitor.

Digital differentiation of non-small cell carcinomas of the lung by the fractal dimension of their epithelial architecture

INTRODUCTION In recent years, differences have emerged in the treatment of squamous and non-squamous non-small cell lung carcinomas (NSCLCs). This highlights the importance of accurate histopathologic classification. However, there remains inter-observer disagreement when making diagnoses based on histology. Fractal dimension (FD) is a mathematical measure of irregularity and complexity of shape. We hypothesize that the FD of carcinoma epithelial architecture can assist in differentiating adenocarcinoma (ADC) from squamous cell carcinoma (SCC) of the lung. METHODS 134 resected (88 ADC and 46 SCC) cases of resected early-stage NSCLC were analyzed. Tissue micro arrays were generated from formalin-fixed paraffin-embedded tissue, stained with pan-cytokeratin, and digitally imaged and the FD of the epithelial structure calculated. Mean FD of ADC and SCC were compared using the independent t-test, partial correlations, and receiver operating characteristic (ROC) analyses. RESULTS A statistically significant difference (p<0.001) between the mean FD of ADC (M=1.70, SD=0.07) and SCC (M=1.78, SD=0.07) was found. Significance remained (p<0.001) when controlling for several possible confounders. ROC analysis demonstrated an area-under-the-curve of 0.81 (p<0.001). CONCLUSIONS The epithelial structure FD of NSCLC has potential as a reproducible and automated measure to help subtype NSCLCs into ADC and SCC. With further image analysis algorithm improvements, fractal analysis may be a component in computerized histomorphological assessments of lung cancer and may provide an adjunct test in differentiating NSCLCs.

Targeting ataxia-telangiectasia mutated deficient malignancies with poly ADP ribose polymerase inhibitors

Small molecule inhibitors of poly ADP ribose polymerase (PARP) have shown considerable promise as therapeutic agents in human malignancies with disruption of the breast and ovarian cancer susceptibility genes BRCA1 or BRCA2 . Evidence is also accumulating that disruption of other genes involved in the detection and/or repair of DNA damage, in particular DNA double strand breaks (DSBs), may also have a synthetic lethal relationship with PARP. One of these is the DNA damage activated protein kinase, ataxia-telangiectasia mutated (ATM). Several studies have shown that ATM deficiency is common in a broad range of hematological and solid malignancies. Here, we discuss the potential for using PARP inhibitors in human cancers with mutation or disruption of ATM .

Predicting PARP inhibitor sensitivity and resistance

The concept of precision therapy in cancer implies an ability to customize treatment according to the molecular makeup of the patient and the tumor. While many pharmaceutical agents are described as targeted therapies, their precise role in cancer treatment is unclear. Often the new drug’s target is well-described, but the precise indication of when it should be used (i.e., a prospectively validated predictive marker) is often not defined. PARP inhibitors exemplify this paradigm well. The molecular target, poly ADP-ribose polymerase 1 (PARP1), and the interaction between drug and target are well-defined, and small-molecule inhibitors of PARP1 (PARP1i) have shown considerable promise for the treatment of BRCA1- and BRCA2-deficient breast, ovarian and prostate cancer.1 Recent work suggests PARP1i may also have utility in the treatment of cancers with deficiencies in other DNA damage response proteins,2 including ATM3-5 and Mre11.6 Nevertheless, experience in triple-negative breast cancer, a limited surrogate for DNA repair deficiency, has tempered enthusiasm for their use, emphasizing that the identification of molecular predictors of PARP1i sensitivity and resistance to guide their use remains a priority. Here, Bartek and colleagues attempt to address this issue directly, describing several key observations.7 First, they extend prior findings to show that depletion of either Nbs1 or Mre11, components of the MRN complex required for activation of ATM and initiation of the homologous recombination DNA double-strand break repair pathway, also sensitize breast cancer cells to PARP1i. However, unlike in cells with depletion or inactivation of ATM, where mutation or depletion of p53 enhances sensitivity to the PARP1i olaparib,4 p53 status had little effect on PARP1i sensitivity in colon cancer cells depleted of Mre11 and/or Nbs1, either alone or in combination with DNA damaging agents, suggesting that Mre11 or Nbs1 deficiency has subtly different effects on PARP1i sensitivity compared with ATM deficiency. Second, the authors show that depletion of 53BP1 promotes PARP1i resistance, consistent with active NHEJ being required for PARP1i-induced cell death.4,8 The successful clinical application of PARP inhibitors will require identification of predictive markers for tumors likely to be susceptible to PARP inhibition. Oplustilova and colleagues7 provide evidence that poly-ADP ribose, the product of PARP activity, could be a potential biomarker of cellular response to PARP inhibition. Finally, the authors address acquired resistance to PARP1i, an evolving problem clinically, by modulation of P-glycoprotein (P-gp). The authors show that the P-gp inhibitor Verapamil overcomes PARP1i efflux attributed to P-gp overexpression, thereby restoring sensitivity to PARP1i.7 Despite addressing these important questions, do these findings herald the arrival of a predictive marker for PARP1i? Unfortunately, the answer is probably not. Although these findings extend our understanding of the potential application of PARP1i to additional DNA repair-deficient cancers, there are several important caveats. The work described was performed on a range of different cell lines in vitro and has not been validated in in vivo models. In addition, the incomplete understanding of the influence of p53 on PARP1i in the context DNA repair deficiency limits its status as a predictor of sensitivity. Finally, overcoming resistance using P-gp inhibitors has had a disappointing course in modulating the efficacy of standard cytotoxic chemotherapy. Unless the third generation P-gp inhibitors are markedly more effective and less toxic, it seems unlikely that this is the best avenue to pursue in improving PARPi utility. As exemplified in HER2-positive breast cancer and in EGFR mutation-positive non-small cell lung cancer, it is a consistent finding that “molecular selection trumps clinical selection.”9 A validated predictive molecular marker can direct targeted therapy, ensuring that patients unlikely to respond are offered more useful intervention, and restrict expensive treatment to those most likely to benefit. While the work of Bartek et al.7 extends our understanding of the role of DNA repair deficiency in PARPi sensitivity, it seems that the subtle nuances of DNA repair pathway modulation make it challenging to develop such a marker for PARP inhibition. In the absence of a functional assay to test tumor DNA repair capacity, more work is required to precisely define which tumor molecular marker (or combination of markers) will best serve this purpose.

Associations of objectively assessed physical activity and sedentary time with health-related quality of life among lung cancer survivors: A quantile regression approach

OBJECTIVES No studies have examined objectively assessed physical activity, sedentary time, and patient-reported outcomes among lung cancer survivors. The objective of this study was to determine associations of objectively assessed moderate-to-vigorous intensity physical activity (MVPA) and sedentary time with health-related quality of life (HRQoL) and fatigue among lung cancer survivors. MATERIALS AND METHOD Lung cancer survivors in Southern Alberta (N = 540) were invited to complete a mailed survey that assessed HRQoL [Functional Assessment of Cancer Therapy-Lung (FACT-L)], physical and functional well-being [Trial Outcome Index (TOI)], and fatigue [Fatigue Scale (FS)]. Physical activity and sedentary time data was collected using an Actigraph® GT3X+ accelerometer that was worn on the hip for seven consecutive days. Quantile regression was used to examine associations of HRQoL and fatigue with physical activity and sedentary time at the 25th, 50th, and 75th HRQoL and fatigue percentiles. RESULTS A total of 127 lung cancer survivors participated for a 24% response rate (Mean age = 71 years; Mean time since diagnosis = 75 months). Total MVPA minutes was positively associated with fewer fatigue symptoms at the 25th percentile (β = 0.16, p = 0.046). Total sedentary time was inversely associated with HRQoL at the 75th percentile (β = -0.07, p = 0.014) and inversely associated with fatigue symptoms at the 50th percentile (β = -0.04, p = 0.009). Total sedentary time was also inversely associated with physical and functional well-being scores at the 25th (β = -0.07, p = 0.045), 50th (β = -0.07, p = 0.004) and 75th (β = -0.04, p = 0.035) percentiles. CONCLUSION Across the HRQoL, fatigue, and physical and functional well-being distributions, sedentary time was inversely associated with HRQoL, fatigue, and physical and functional well-being in lung cancer survivors. Small associations were observed between MVPA and fatigue, but no associations emerged with HRQoL or physical and functional well-being.

Abstract A89: Gender and racial disparities in non-small cell lung cancer: A systematic review

Lung cancer is the leading cause of cancer death in the U.S. and remains the least-funded cancer in North America. Many studies addressed disparities in lung cancer incidence rate among the races; however, few studies described the effect of both race and gender in the risk of manifesting this disease. These studies lack consensus for both the etiology and the magnitude of gender-based disparities and their impact on disease development on specific racial groups. These unknown race-associated characteristics between men and women might adversely affect the improvement of current therapies and patient outcomes. Characterizing gender as a possible risk modifier in lung cancer development among certain ethnic groups may aid in the development of targeted agents that improve patient outcomes. This study aimed to investigate the global pattern of gender-based disparities in incidence of lung cancer and describe the etiologic factors associated with different racial groups in non-small cell lung cancer (NSCLC), since it comprises 85% of all diagnosed cases. This aim was accomplished by analyzing data scrutinized using a systematic review approach for studies published between 1996 and 2016. We found a statistically significant effect of race on lung cancer incidence rate, and this effect varies by gender. We also found that certain races are more prone to develop adenocarcinoma in their histology than others, regardless of their sex. In addition, we found that Asian women have higher rates of NSCLC regardless of their living environment. Our findings also show that the number of cases of NSCLC is rising among women of all races, regardless of their smoking status. By visualizing NSCLC pattern in both men and women among different countries and racial groups, we stimulate future findings to establish efficacious preventative strategies and will stimulate research advancements toward sex- and racial-designed diagnostics, including alternative treatments that could reduce the manifestation of this disease. Note: This abstract was not presented at the conference. Citation Format: Noor Alsaadoun, Karen Kopciuk, Desiree Hao, Karl Riabowol, D. Morley Hollenberg, D. Gwyn Bebb. Gender and racial disparities in non-small cell lung cancer: A systematic review [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr A89.