Margaret M. Kozak

Distinct p53 Transcriptional Programs Dictate Acute DNA-Damage Responses and Tumor Suppression

The molecular basis for p53-mediated tumor suppression remains unclear. Here, to elucidate mechanisms of p53 tumor suppression, we use knockin mice expressing an allelic series of p53 transcriptional activation mutants. Microarray analysis reveals that one mutant, p53(25,26), is severely compromised for transactivation of most p53 target genes, and, moreover, p53(25,26) cannot induce G(1)-arrest or apoptosis in response to acute DNA damage. Surprisingly, p53(25,26) retains robust activity in senescence and tumor suppression, indicating that efficient transactivation of the majority of known p53 targets is dispensable for these pathways. In contrast, the transactivation-dead p53(25,26,53,54) mutant cannot induce senescence or inhibit tumorigenesis, like p53 nullizygosity. Thus, p53 transactivation is essential for tumor suppression but, intriguingly, in association with a small set of novel p53 target genes. Together, our studies distinguish the p53 transcriptional programs involved in acute DNA-damage responses and tumor suppression-a critical goal for designing therapeutics that block p53-dependent side effects of chemotherapy without compromising p53 tumor suppression.

Stereotactic body radiotherapy for colorectal liver metastases: A pooled analysis

This study was undertaken to determine outcomes of stereotactic body radiotherapy for colorectal liver metastases in a pooled patient cohort.

Inappropriate p53 activation during development induces features of CHARGE syndrome

CHARGE syndrome is a multiple anomaly disorder in which patients present with a variety of phenotypes, including ocular coloboma, heart defects, choanal atresia, retarded growth and development, genitourinary hypoplasia and ear abnormalities. Despite 70–90% of CHARGE syndrome cases resulting from mutations in the gene CHD7, which encodes an ATP-dependent chromatin remodeller, the pathways underlying the diverse phenotypes remain poorly understood. Surprisingly, our studies of a knock-in mutant mouse strain that expresses a stabilized and transcriptionally dead variant of the tumour-suppressor protein p53 (p5325,26,53,54), along with a wild-type allele of p53 (also known as Trp53), revealed late-gestational embryonic lethality associated with a host of phenotypes that are characteristic of CHARGE syndrome, including coloboma, inner and outer ear malformations, heart outflow tract defects and craniofacial defects. We found that the p5325,26,53,54 mutant protein stabilized and hyperactivated wild-type p53, which then inappropriately induced its target genes and triggered cell-cycle arrest or apoptosis during development. Importantly, these phenotypes were only observed with a wild-type p53 allele, as p5325,26,53,54/− embryos were fully viable. Furthermore, we found that CHD7 can bind to the p53 promoter, thereby negatively regulating p53 expression, and that CHD7 loss in mouse neural crest cells or samples from patients with CHARGE syndrome results in p53 activation. Strikingly, we found that p53 heterozygosity partially rescued the phenotypes in Chd7-null mouse embryos, demonstrating that p53 contributes to the phenotypes that result from CHD7 loss. Thus, inappropriate p53 activation during development can promote CHARGE phenotypes, supporting the idea that p53 has a critical role in developmental syndromes and providing important insight into the mechanisms underlying CHARGE syndrome.

Intensity-modulated radiotherapy for oral cavity squamous cell carcinoma: Patterns of failure and predictors of local control

PURPOSE Few studies have evaluated the use of intensity-modulated radiotherapy (IMRT) for squamous cell carcinoma (SCC) of the oral cavity (OC). We report clinical outcomes and failure patterns for these patients. METHODS AND MATERIALS Between October 2002 and June 2009, 37 patients with newly diagnosed SCC of the OC underwent postoperative (30) or definitive (7) IMRT. Twenty-five patients (66%) received systemic therapy. The median follow-up was 38 months (range, 10-87 months). The median interval from surgery to RT was 5.9 weeks (range, 2.1-10.7 weeks). RESULTS Thirteen patients experienced local-regional failure at a median of 8.1 months (range, 2.4-31.9 months), and 2 additional patients experienced local recurrence between surgery and RT. Seven local failures occurred in-field (one with simultaneous nodal and distant disease) and two at the margin. Four regional failures occurred, two in-field and two out-of-field, one with synchronous metastases. Six patients experienced distant failure. The 3-year actuarial estimates of local control, local-regional control, freedom from distant metastasis, and overall survival were 67%, 53%, 81%, and 60% among postoperative patients, respectively, and 60%, 60%, 71%, and 57% among definitive patients. Four patients developed Grade ≥ 2 chronic toxicity. Increased surgery to RT interval predicted for decreased LRC (p = 0.04). CONCLUSIONS Local-regional control for SCC of the OC treated with IMRT with or without surgery remains unsatisfactory. Definitive and postoperative IMRT have favorable toxicity profiles. A surgery-to-RT interval of < 6 weeks improves local-regional control. The predominant failure pattern was local, suggesting that both improvements in target delineation and radiosensitization and/or dose escalation are needed.

Impact of Chemotherapy on Normal Tissue Complication Probability Models of Acute Hematologic Toxicity in Patients Receiving Pelvic Intensity Modulated Radiation Therapy

PURPOSE To determine how chemotherapy agents affect radiation dose parameters that correlate with acute hematologic toxicity (HT) in patients treated with pelvic intensity modulated radiation therapy (P-IMRT) and concurrent chemotherapy. METHODS AND MATERIALS We assessed HT in 141 patients who received P-IMRT for anal, gynecologic, rectal, or prostate cancers, 95 of whom received concurrent chemotherapy. Patients were separated into 4 groups: mitomycin (MMC) + 5-fluorouracil (5FU, 37 of 141), platinum ± 5FU (Cis, 32 of 141), 5FU (26 of 141), and P-IMRT alone (46 of 141). The pelvic bone was contoured as a surrogate for pelvic bone marrow (PBM) and divided into subsites: ilium, lower pelvis, and lumbosacral spine (LSS). The volumes of each region receiving 5-40 Gy were calculated. The endpoint for HT was grade ≥3 (HT3+) leukopenia, neutropenia or thrombocytopenia. Normal tissue complication probability was calculated using the Lyman-Kutcher-Burman model. Logistic regression was used to analyze association between HT3+ and dosimetric parameters. RESULTS Twenty-six patients experienced HT3+: 10 of 37 (27%) MMC, 14 of 32 (44%) Cis, 2 of 26 (8%) 5FU, and 0 of 46 P-IMRT. PBM dosimetric parameters were correlated with HT3+ in the MMC group but not in the Cis group. LSS dosimetric parameters were well correlated with HT3+ in both the MMC and Cis groups. Constrained optimization (0<n≤ 1) of the Lyman-Kutcher-Burman model resulted in n=1, m = 0.11, TD50 = 31 Gy for LSS in the MMC group and n=1, m = 0.27, TD50 = 35 Gy for LSS in the Cis group. CONCLUSIONS The incidence of HT3+ depends on type of chemotherapy received. Patients receiving P-IMRT ± 5FU have better bone marrow tolerance than those receiving irradiation concurrent with either Cis or MMC. Treatment with MMC has a lower TD50 and more steeply rising normal tissue complication probability curve compared with treatment with Cis. Dose tolerance of PBM and the LSS subsite may be lower for patients treated with MMC compared with Cis.

Tumor Volume as a Potential Imaging-Based Risk-Stratification Factor in Trimodality Therapy for Locally Advanced Non-small Cell Lung Cancer

Introduction:The role of trimodality therapy for locally advanced non-small cell lung cancer (NSCLC) continues to be defined. We hypothesized that imaging parameters on pre- and postradiation positron emission tomography (PET)-computed tomography (CT) imaging are prognostic for outcome after preoperative chemoradiotherapy (CRT)/resection/consolidation chemotherapy and could help risk-stratify patients in clinical trials. Methods:We enrolled 13 patients on a prospective clinical trial of trimodality therapy for resectable locally advanced NSCLC. PET-CT was acquired for radiation planning and after 45 Gy. Gross tumor volume (GTV) and standardized uptake value were measured at pre- and post-CRT time points and correlated with nodal pathologic complete response, loco-regional and/or distant progression, and overall survival. In addition, we evaluated the performance of automatic deformable image registration (ADIR) software for volumetric response assessment. Results:All patients responded with average total GTV reductions after 45 Gy of 43% (range: 27–64%). Pre- and post-CRT GTVs were highly correlated (R2 = 0.9), and their respective median values divided the patients into the same two groups. ADIR measurements agreed closely with manually segmented post-CRT GTVs. Patients with GTV ≥ median (137 ml pre-CRT and 67 ml post-CRT) had 3-year progression-free survival (PFS) of 14% versus 75% for GTV less than median, a significant difference (p = 0.049). Pre- and post-CRT PET-standardized uptake value did not correlate significantly with pathologic complete response, PFS, or overall survival. Conclusions:Preoperative CRT with carboplatin/docetaxel/45 Gy resulted in excellent response rates. In this exploratory analysis, pre- and post-CRT GTV predicted PFS in trimodality therapy, consistent with our earlier studies in a broader cohort of NSCLC. ADIR seems robust enough for volumetric response assessment in clinical trials.

Statin and Metformin Use Prolongs Survival in Patients With Resectable Pancreatic Cancer.

Objectives The aim of this study was to investigate the impact of statin and metformin therapy on disease outcome for patients with pancreatic ductal adenocarcinoma (PDAC). Methods This retrospective study included 171 PDAC patients who underwent surgical resection at the Stanford Cancer Institute between 1998 and 2013. No patients received neoadjuvant therapy. Statin and metformin use was defined as use during initial consult and continuing upon discharge from the hospital after surgery. Dose of each medication was recorded, as was the type of statin taken. Results The median follow-up for all patients was 11.23 months (range, 0.2–105.0 months). Among the 171 patients included in our analysis, 18 patients (10.5%) took metformin and 34 patients (19.9%) took statins. Statin use was associated with better overall survival (OS) in patients with PDAC (P = 0.011). Metformin use was also associated with better OS (P = 0.035). The use of statins remained significant on multivariate analysis for OS (P = 0.014; hazards ratio, 0.33; 95% confidence interval, 0.139–0.799), but metformin use did not (P = 0.33; hazards ratio 0.60, 95% confidence interval, 0.211–1.675). Conclusions Statin and metformin use is associated with improved OS in patients with resectable PDAC. These medications should be further investigated for possible long-term use in the general population.

Albumin and Neutrophil-Lymphocyte Ratio (NLR) Predict Survival in Patients With Pancreatic Adenocarcinoma Treated With SBRT

Purpose: To determine if pretreatment nutritional status and inflammatory markers correlate with survival in patients with locally advanced pancreatic adenocarcinoma treated with stereotactic body radiotherapy (SBRT). Materials and Methods: We retrospectively reviewed 208 patients with newly diagnosed, locally advanced pancreatic adenocarcinoma treated with SBRT at our institution from 2002 to 2014. Laboratory values were collected before SBRT, including hemoglobin, platelets, albumin, red blood cell, white blood cell, neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio, and tumor markers CA 19-9 and CEA. Patients were followed every 3 months with computed tomography (CT) and/or positron emission tomography-CT imaging to monitor for local recurrence and overall survival (OS). Results: Median follow-up after SBRT was 7.5 months (interquartile range, 4.6 to 12.0 mo) for all patients. Median OS for patients with NLR>5 compared with NLR⩽5 was 6.9 and 8.5 months, respectively (P=0.0057). On univariate analysis, receipt of chemotherapy (P=0.05, hazard ratio [HR]=0.69), increased albumin (P=0.002, HR=0.64), increased red blood cell (P=0.05, HR=0.75), increased lymphocyte count (P=0.002, HR=0.66), decreased CEA (P=0.01, HR=0.96), and NLR⩽5 (P=0.01, HR=0.65) correlated with improved OS. On multivariate analysis, higher albumin (P=0.03, HR=0.70), receipt of chemotherapy (P=0.007, HR=0.56), and NLR⩽5 (P=0.02, HR=0.66) correlated with better survival. Conclusions: Preradiotherapy low albumin levels and NLR>5 correlate with decreased survival in patients with locally advanced pancreatic adenocarcinoma treated with SBRT, indicating the prognostic value of systemic inflammatory markers (such as NLR) and a role of nutritional supplementation to improve outcomes in these patients. Further investigation is warranted.

The Prognostic Significance of Pretreatment Hematologic Parameters in Patients Undergoing Resection for Colorectal Cancer.

Objectives: The prognostic value of several hematologic parameters, including platelet, lymphocyte, and neutrophil counts, has been studied in a variety of solid tumors. In this study, we examined the significance of inflammatory markers and their prognostic implications in patients with colorectal cancer (CRC). Materials and Methods: Patients with stage I-III CRC who underwent surgical resection at the Stanford Cancer Institute between 2005 and 2009 were included. Patients were excluded if they did not have preoperative complete blood counts performed within 1 month of surgical resection, underwent preoperative chemotherapy or radiation, had metastatic disease at diagnosis, or had another previous malignancy. We included 129 eligible patients with available preoperative complete blood counts in the final analysis. Results: A preoperative neutrophil-to-lymphocyte ratio of>3.3 was significantly associated with worse disease-free (DFS) and overall survival (OS) (P=0.009, 0.003), as was a preoperative lymphocyte-to-monocyte ratio of ⩽2.6 (P=0.01, 0.002). Preoperative lymphopenia (P=0.002) was associated with worse OS but not DFS (P=0.09). In addition, preoperative thrombocytosis was associated with worse DFS (P=0.006) and OS (P=0.010). Preoperative leukocytosis was associated with worse OS (P=0.048) but not DFS (P=0.49). Preoperative hemoglobin was neither associated with OS (P=0.24) or DFS (P=0.15). Conclusions: Pretreatment lymphopenia, thrombocytosis, a decreased lymphocyte-to-monocyte ratio, and an elevated neutrophil-to-lymphocyte ratio independently predict for worse OS in patients with CRC.

Smad4 inactivation predicts for worse prognosis and response to fluorouracil-based treatment in colorectal cancer

Aims To determine whether expression of Smad4, a tumour suppressor found to be absent in 10% of colorectal cancer (CRC), is associated with outcomes in patients with CRC. Methods Tumour samples from 241 consecutive patients with CRC who underwent upfront colon resection between 2005 and 2009 were obtained. Triplicate tissue cores from resected primary colon tumours and matched normal controls were used to construct the tissue microarrays (TMAs). We examined the expression of Smad4 using immunohistochemistry. Clinicopathological records were obtained for all patients. TMAs were reviewed by two pathologists and scored as either ‘positive’ or ‘negative’ for nuclear staining. In total, 21 of 241 tumours (8.6%) were Smad4 negative. Results Loss of Smad4 expression correlated with significantly worse overall survival (OS) (p=0.011) and disease-free survival (DFS) (p=0.024). Patients with loss of Smad4 expression had a median OS of 31 months compared with 89 months positive Smad4 expression. Loss of Smad4 remained significant on multivariate analysis for OS (p=0.0097). In patients with node-positive disease, loss of Smad4 predicts for worse DFS (p=0.012). In patients with metastatic and recurrent disease, Smad4 loss predicts for worse OS (p=0.012). Of the patients that received capecitabine over the course of their treatment, those with Smad4 loss (n=13) had significantly worse DFS (p=0.003) and OS (p=0.0007). Conclusions Loss of Smad4 expression is associated with worse DFS and OS in multiple subsets of patients with CRC. Further studies are required to validate our findings and ascertain the role of Smad4 status in the management of this disease.