Abstract 4794: Deciphering tumor recurrence post-therapy: Interactions between the tumor microenvironment and therapy-induced senescent glioblastoma

Glioblastoma (GBM) remains one of the most lethal forms of cancer due, in part, to the capacity of tumor cells to persist during therapy and then recover. Understanding how these residual tumor cells survive is therefore imperative to developing more effective treatment strategies. We have demonstrated that GBM cells, including those from patient-derived xenografts, undergo a state of therapy-induced senescence (TIS) rather than cell death following temozolomide (TMZ) and radiation (IR). Both TMZ and IR treatment at physiologically relevant doses result in elevated senescence-associated-β-galactosidase, altered morphology, p21 induction, and increased expression of the senescence-associated-heterochromatic-foci marker H3K9Me3. Further, despite TIS-induction in a majority of the residual cells post-treatment, GBM viable cell number increases after a prolonged stasis, indicating that populations are capable of reentering a proliferative state. However, our current understanding of how the tumor microenvironment influences this growth arrest and subsequent proliferative recovery is underdeveloped. We aim to bridge that gap by investigating the paracrine communications between astrocytes and GBM cells undergoing IR-induced senescence in order to identify how these interactions foster disease progression. Current studies are focused on evaluating the effect of astrocytes on the induction and durability of TIS in GBM cells. Proteomic studies will be pursued to characterize the secretome of astrocyte-GBM co-cultures and identify factors that drive GBM senescent response to IR. Finally, based on preliminary data demonstrating that normal astrocytes are also damaged by IR, we will undertake mechanistic studies to understand how cell-intrinsic events within the astrocyte population drive extrinsic-influence on GBM cells. We anticipate that these identified signaling events may serve as potential therapeutic targets.

Citation Format: Valerie DeLuca, Priya Digumarti, Michael E. Berens. Deciphering tumor recurrence post-therapy: Interactions between the tumor microenvironment and therapy-induced senescent glioblastoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4794.

Somatic inactivating PTPRJ mutations and dysregulated pathways identified in canine malignant melanoma by integrated comparative genomic analysis

Canine malignant melanoma, a significant cause of mortality in domestic dogs, is a powerful comparative model for human melanoma, but little is known about its genetic etiology. We mapped the genomic landscape of canine melanoma through multi-platform analysis of 37 tumors (31 mucosal, 3 acral, 2 cutaneous, and 1 uveal) and 17 matching constitutional samples including long- and short-insert whole genome sequencing, RNA sequencing, array comparative genomic hybridization, single nucleotide polymorphism array, and targeted Sanger sequencing analyses. We identified novel predominantly truncating mutations in the putative tumor suppressor gene PTPRJ in 19% of cases. No BRAF mutations were detected, but activating RAS mutations (24% of cases) occurred in conserved hotspots in all cutaneous and acral and 13% of mucosal subtypes. MDM2 amplifications (24%) and TP53 mutations (19%) were mutually exclusive. Additional low-frequency recurrent alterations were observed amidst low point mutation rates, an absence of ultraviolet light mutational signatures, and an abundance of copy number and structural alterations. Mutations that modulate cell proliferation and cell cycle control were common and highlight therapeutic axes such as MEK and MDM2 inhibition. This mutational landscape resembles that seen in BRAF wild-type and sun-shielded human melanoma subtypes. Overall, these data inform biological comparisons between canine and human melanoma while suggesting actionable targets in both species.

The mechanism underlying the hypocholesterolemic effect of chronic fish oil feeding in rats is not due to increased excretion of dietary cholesterol

The role of the excretion of dietary cholesterol in the hypocholesterolaemic effect of chronic fish oil feeding in rats was investigated. The hepatic uptake and processing of [3H]cholesterol carried in chylomicrons derived from fish oil was studied in vivo in rats fed a low fat diet or a diet supplemented with fish oil for 21 days. In addition, the effects of the fish oil diet on cholesterol esterification, cholesteryl ester hydrolysis, bile acid synthesis and biliary lipid secretion were determined. In rats fed the fish oil as compared to the low fat diet, the uptake of [3H]cholesterol from the blood and its secretion into bile as bile acids was significantly slower, and this was entirely due to a decrease in the bile acid fraction. Biliary bile acid mass secretion was unchanged by fish oil feeding, while biliary cholesterol and phospholipid secretion was increased. No significant differences were observed either in the expression of mRNA for cholesterol 7alpha hydroxylase or the secretion of bile acids into bile after 20 h biliary drainage between the fish oil and low fat diet groups, suggesting that bile acid synthesis is not affected. These results indicate that the access of chylomicron cholesterol to the hepatic substrate pool for bile acid formation is decreased in the fish oil fed rats, and this, together with its slower uptake from the blood, accounts for the retardation of its excretion via the bile. Thus, the hypocholesterolemic effect of dietary fish oil in rats is not due to more rapid metabolism of cholesterol originating from the diet.

The benefit of hormone replacement therapy on bone mass is greater at the vertebral body than posterior processes or proximal femur

The aim of this study was to determine whether the higher vertebral bone mass in women receiving hormone replacement therapy (HRT) is confined to the trabecular rich vertebral body rather than the predominantly cortical posterior processes, and to determine whether the protective effect of HRT at the proximal femur, a predominantly cortical site, is less than at the spine. Bone mass (g) of the third lumbar vertebra (total, vertebral body and posterior processes, measured by lateral scanning), and bone mineral density (g/cm2) of the femoral neck, Ward's triangle, and trochanter were measured using dual X-ray absorptiometry in a cross-sectional study of 71 women receiving HRT for 5.7 +/- 0.4 years (mean +/- SEM), ranging from 1 to 21 years, 69 age-matched controls, and 42 premenopausal controls aged 20 to 40 years. Relative to untreated postmenopausal controls, total bone mass of the third lumbar vertebra (body plus posterior processes) by postero-anterior (PA) scanning was 0.4 +/- 0.1 SD or 9.6 +/- 3.0% higher in HRT treated women (p < 0.01). By lateral scanning, total bone mass was higher than age-matched controls (z score 0.4 +/- 0.1 SD or 11.2 +/- 3.4%, p < 0.01). This difference was confined to the vertebral body (z score 0.6 +/- 0.1 SD, p < 0.001), which was 17.1 +/- 3.3% higher than in age-matched controls (p < 0.001). Bone mass of the posterior processes was no higher [z score 0.1 +/- 0.1, not significant (NS)]. The deficit at the vertebral body in HRT-treated women, relative to premenopausal controls, was half the deficit at the vertebral body in untreated postmenopausal women (t score -0.7 +/- 0.1 vs. -1.4 +/- 0.1 SD, respectively; p < 0.001) but no less at the posterior processes (t score -1.6 +/- 0.2 vs. -1.9 +/- 0.2 SD, respectively; NS). Similarly, the deficit in the vertebral body in the HRT treated group was half the deficit at their posterior processes (t score -0.7 +/- 0.1 SD vs. -1.6 +/- 0.2, respectively; p < 0.001). In HRT-treated women, bone mass diminished significantly with age at the posterior processes (r = -0.31, p < 0.01), but not at the vertebral body (r = -0.21, p = 0.07). Bone mass diminished significantly with age at the vertebral body and posterior processes in untreated women (r = -0.55, p < 0.001; r = -0.45, p < 0.001, respectively). Bone density (g/cm2) diminished at all femoral sites with advancing age in HRT-treated women. A protective effect was seen at the femoral neck and Ward's triangle, but not trochanter (z score 0.2 +/- 0.1, p = 0.06; 0.3 +/- 0.1, p < 0.05; 0.0 +/- 0.1, NS, respectively). In conclusion, the protective effect of HRT against bone loss at the vertebral body, the site of fracture in osteoporosis, may be underestimated by PA scanning. The greater benefit at the vertebral body, and more modest effect at the proximal femur, suggests that HRT may be a more effective means of reducing the risk of spine than hip fractures.

Bone mass, areal, and volumetric bone density are equally accurate, sensitive, and specific surrogates of the breaking strength of the vertebral body: an in vitro study

The validity of the bone mineral density (BMD) measurement depends on its accuracy as a predictor of the breaking strength of bone. As the breaking strength is proportional to the square of the apparent density, a small error in the calculation of BMD may result in a larger error in the predicted bone strength. The aims of this study were (i) to determine whether inaccuracies in the measurement of the dimensions, projected area, and volume of the vertebral body (used to derive the areal and volumetric BMD) result in errors in the predicted breaking strength and (ii) to compare the accuracy, sensitivity, and specificity of bone mineral content (BMC), areal BMD, volumetric BMD, and volumetric bone mineral apparent density (BMAD) as surrogates of bone strength. We measured the BMC (by densitometry), dimensions and volume (using calipers, densitometry, the Carter et al. and Peel and Eastell methods), and breaking strength (using the Instron 1114 apparatus, Newtons, N) of 22 vertebral body specimens. All methods resulted in errors in height, width, and depth between -11.3 +/- 1.0 and 30.4 +/- 1.8% relative to the "gold" standard caliper method. The vertebral body volume (of 38.0 +/- 1.2 cm3) measured by submersion was used as the gold standard to derive the volumetric BMD gold standard (of 0.162 +/- 0.01 g/cm3). All methods, except the Peel and Eastell method, resulted in errors ranging between -10.7 +/- 1.5 and 56.9 +/- 3.4% in vertebral body volume and -35.6 +/- 1.5 to 12.6 +/- 1.8% in volumetric BMD (all p < 0.0005). The same absolute value for volumetric BMD predicted a breaking strength that differed according to the method used to derive BMD. For example, a volumetric BMD of 0.162 g/cm3 predicted a breaking strength of 6208 N (submersion method), 5473 N (caliper method), 6095 N (Peel and Eastell method), 7697 N (DXA method), and 9470 N (Carter et al. method). The mean volumetric BMD derived by each method differed (0.181, 0.165, 0.133, and 0.104 g/cm3, respectively). However, all were accurate; each predicted a similar breaking strength (6177, 6217, 6209, and 6221 N respectively). Likewise, breaking strengths predicted by the mean BMC, areal BMD by calipers, and areal BMD by dual-energy X-ray absorptiometry (DXA) were 6267, 6214, and 6244 N, respectively. The methods were equally sensitive; a 1 standard deviation (SD) decrease in volumetric BMD resulted in a similar decrease in the breaking strength of 1818 (caliper), 2080 (Peel and Eastell), 2001 (DXA), and 1625 N (BMAD by Carter et al). A 1 SD decrease in BMC, areal BMD (using calipers) and areal BMD (using DXA) predicted a decrease in the breaking strength of 2019, 1738, and 1825 N, respectively. All methods were equally specific; the variance in bone strength explained by bone mass did not differ for volumetric BMD (38-61% depending on the method), BMC (58%), or areal BMD (48%). In conclusion, despite errors in the measurement of the dimensions of the vertebral body, bone mass, areal, and volumetric bone density are equally accurate, sensitive, and specific surrogates of the breaking strength of bone in vitro.

Purification and cDNA cloning of anthranilate synthase from Ruta graveolens: modes of expression and properties of native and recombinant enzymes

Ruta graveolens utilizes anthranilate synthase (AS) for the synthesis both of tryptophan in primary metabolism and acridone alkaloids in secondary metabolism. AS has been purified from plants and cell cultures of R. graveolens 670- and 1700-fold, respectively. Glutamine- and ammonia-dependent AS activities were strictly co-purified in all steps. Through cDNA cloning and complementation of Escherichia coli deletion mutants defective for AS, it is shown that young Ruta plants express two genes for functional AS alpha subunits, AS alpha 1 and AS alpha 2. The data indicate that AS alpha from Ruta requires an AS beta subunit with a native molecular weight of 60-65 kDa for the glutamine-dependent reaction. Protein synthesized in vitro from cloned cDNA is processed upon import into isolated chloroplasts, indicating that mature AS alpha subunits are active in plastids in vivo. AS alpha 1 and AS alpha 2 are constitutively expressed in Ruta cell cultures, but AS alpha 1 steady-state mRNA levels are increased 100-fold 6 h subsequent to elicitation whereas AS alpha 2 expression remains constitutive. Increased AS alpha 1 transcription corresponds to elicitor-induced alkaloid accumulation. The data indicate that Ruta regulates anthranilate flux into primary and secondary metabolism through differential regulation of AS genes specific to these pathways.

Molecular characterization of two plant flavonol sulfotransferases

cDNA clones coding for flavonol 3- and 4'-sulfotransferases (STs) were isolated by antibody screening of a cDNA expression library produced from poly(A)+ RNA extracted from terminal buds of Flaveria chloraefolia. Sequence analysis revealed full-length cDNA clones with open reading frames of 933 and 960 base pairs, which encode polypeptides containing 311 and 320 amino acids, respectively. This corresponds to a molecular mass of 36,442 Da for the 3-ST and 37,212 Da for the 4'-ST. Expression of these clones in Escherichia coli led to the synthesis of beta-galactosidase-ST fusion proteins having the same substrate and position specificities as those for the 3- and 4'-flavonol ST enzymes isolated from the plant. Comparison of the deduced amino acid sequence of the two clones revealed an overall identity of 69% in 311 amino acid residues. The two flavonol STs of F. chloraefolia also shared significant sequence similarities with steroid and aryl STs found in animal tissues and with the senescence marker protein 2 isolated from rat liver, suggesting an evolutionary link between plant and animal STs.

Treatment of benign chronic gastric ulcer with ranitidine. A randomized, double-blind, and placebo-controlled six week trial

A randomized, multicenter, double-blind, placebo-controlled study was conducted to determine whether ranitidine 150 mg b.i.d. for 6 weeks would expedite endoscopic healing or relief of symptoms in patients with benign gastric ulcer. Of 203 patients enrolled, 101 received ranitidine and 102 received placebo. Endoscopic evaluations were conducted at baseline and at 2 and 6 weeks. At 6 weeks 68% of the patients treated with ranitidine had healed compared with 53% in the placebo group (p = 0.02). In those patients who had not healed by 6 weeks, ranitidine provided greater relief from pain than placebo. More patients in the placebo group dropped out of the study because of worsening symptoms (13 versus 4, p = 0.04). No differences in laboratory abnormalities or incidence of adverse events were detected between the two study groups. These results indicate that ranitidine 150 mg b.i.d. is superior to placebo in the treatment of benign gastric ulcer.

The association of histologic gastritis with gastroesophageal reflux and delayed gastric emptying

The aims of this study were to: 1) investigate the incidence of histologic gastritis in patients with gastroesophageal reflux (GER); 2) ascertain if gastritis in GER patients could be correlated with impaired gastric emptying; and 3) determine if the presence of histologic antral gastritis correlated with other parameters of esophageal and gastric function. Twenty-three GER patients, mean age 53.3 years (range 28-68 years) with subjective and objective evidence for GER; and 20 normal subjects (13 males and seven females), mean age 28.7 years (range 19-46 years), underwent upper gastrointestinal endoscopy. Antral biopsies obtained from the greater curvature were graded as: 0 = normal; 1 = chronic gastritis; 2 = chronic active gastritis; and 3 = chronic atrophic gastritis. All patients underwent a gastric emptying study using an isotope-labeled semisolid meal. Eighteen of the 23 GER patients (78%) had histologic gastritis compared to two (10%) of the normals. No subject had endoscopic evidence of gastritis. Gradings of histologic gastritis were significantly (p less than 0.05) correlated with delayed gastric emptying. Twelve GER patients had severe gastritis (grades 2 or 3) and their gastric emptying, 79.7% +/- 5.8 (mean +/- S.E.M.) retention of isotope at 90 minutes after the meal, was significantly slower (p less than 0.01) than the 11 GER patients with either grade 0 or 1 gastritis, 56.1% +/- 5.9 retention, or the normal subjects, 51.8% +/- 1.7. We conclude that: 1) histologic gastritis is associated with GER disease; and 2) slowing of gastric emptying can be significantly correlated with increased severity of histologic gastritis in GER patients.

Reassessment of esophageal histology in normal subjects: a comparison of suction and endoscopic techniques

We have examined esophageal biopsies from 18 asymptomatic volunteers. These normal subjects were also evaluated by esophageal manometry with determination of motor function of the esophagus and lower esophageal sphincter pressure, a modified Bernstein acid infusion test, and a basal pH reflux test. In 12 subjects, biopsies were obtained by suction technique; the remaining six had pinch biopsies performed during upper gastrointestinal endoscopy. Forty-nine (92.5%) of the 53 suction biopsies yielded tissue as deep as muscularis mucosa or at least ample amounts of lamina propria. In contrast, all 28 endoscopic biopsies yielded squamous epithelium only. Moreover, suction biopsies were generally well-oriented (83%), whereas endoscopic biopsies were less commonly well-oriented (35.7%). All volunteer subjects had a negative acid reflux test confirming the absence of latent or asymptomatic reflux. Only one subject (5.6%) had biopsies which met histologic criteria for gastroesophageal reflux. We conclude that: 1) more tissue, more information, and better orientation is achieved with suction than with endoscopic biopsies of the esophagus; 2) the low false-positive rate observed in volunteers in whom gastroesophageal reflux was objectively excluded emphasizes the value of esophageal biopsy as a reliable index in the evaluation of gastroesophageal reflux.

Gastroduodenitis. A broader concept of peptic ulcer disease

To evaluate the frequency and type of gastroduodenal mucosal inflammatory changes in patients with symptomatic acid peptic disease and nonulcer dyspepsia, 100 patients with gastrointestinal symptoms indicative of acid peptic disease or dyspepsia and 10 control subjects were clinically evaluated and underwent radiographic, endoscopic, and biopsy studies of the stomach and duodenum. Clinical evaluation revealed that of the 100 patients, 61% had classic and 39% had atypical manifestations of acid peptic (ulcer) disease. Endoscopic and histologic evaluation revealed that 25 patients had peptic ulcer craters, 86-90% of whom had associated gastroduodenitis. Thirty-nine patients had acute and 20 patients had chronic gastroduodenitis without ulcer crater. Twelve symptomatic patients had no histologic changes in the gastroduodenal mucosa. Two of the ten control subjects had mild gastritis. In the 61% of the patients with classic manifestations of peptic ulcer disease, we could not clinically distinguish the 24 patients with craters, (40% of the classic group) from the 25 patients with acute gastroduodenitis without craters (41% of the classic group). As a result of this study of our group of patients, we believe that gastroduodenitis can be symptomatic and may present with the same manifestations as peptic ulcer crater. Further study will be required to determine whether gastroduodenitis is an independent entity or part of the spectrum of acid peptic (ulcer) disease.

Respiratory pathways and fat synthesis in the developing castor oil seed

During castor oil seed development, changes occur in the activities of enzymes involved in fatty acid biosynthesis, glycolysis, and the pentose phosphate pathways. The activities of acetyl-CoA carboxylase, phosphofructokinase, pyruvate kinase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase per seed increase during the phase of rapid oil synthesis in the endosperm. As the seed matures and the rate of fatty acid synthesis decreases, there is a corresponding diminution in the activities of these enzymes. An indication of the metabolic capacity of the plastids was determined by monitoring the ribulose-1,5-bisphosphate carboxylase activity in the endosperm.