Optimal therapeutic targeting by HDAC inhibition in biopsy-derived treatment-naïve diffuse midline glioma models

BACKGROUND

Diffuse midline gliomas (DMGs), including diffuse intrinsic pontine gliomas (DIPGs), have a dismal prognosis, with less than 2% surviving 5 years postdiagnosis. The majority of DIPGs and all DMGs harbor mutations altering the epigenetic regulatory histone tail (H3 K27M). Investigations addressing DMG epigenetics have identified a few promising drugs, including the HDAC inhibitor (HDACi) panobinostat. Here, we use clinically relevant DMG models to identify and validate other effective HDACi and their biomarkers of response.

METHODS

HDAC inhibitors were tested across biopsy-derived treatment-naïve in vitro and in vivo DMG models with biologically relevant radiation resistance. RNA sequencing was performed to define and compare drug efficacy and to map predictive biomarkers of response.

RESULTS

Quisinostat and romidepsin showed efficacy with low nanomolar half-maximal inhibitory concentration (IC50) values (~50 and ~5 nM, respectively). Comparative transcriptome analyses across quisinostat, romidepsin, and panobinostat showed a greater degree of shared biological effects between quisinostat and panobinostat, and less overlap with romidepsin. However, some transcriptional changes were consistent across all 3 drugs at similar biologically effective doses, such as overexpression of troponin T1 slow skeletal type (TNNT1) and downregulation of collagen type 20 alpha 1 chain (COL20A1), identifying these as potential vulnerabilities or on-target biomarkers in DMG. Quisinostat and romidepsin significantly (P < 0.0001) inhibited in vivo tumor growth.

CONCLUSIONS

Our data highlight the utility of treatment-naïve biopsy-derived models; establishes quisinostat and romidepsin as effective in vivo; illuminates potential mechanisms and/or biomarkers of DMG cell lethality due to HDAC inhibition; and emphasizes the need for brain tumor-penetrant versions of potentially efficacious agents.

A Protocol for the Generation of Treatment-naïve Biopsy-derived Diffuse Intrinsic Pontine Glioma and Diffuse Midline Glioma Models

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal tumor of the brainstem, most commonly affecting young children. Due to its location, surgical resection is not achievable, but consideration of a biopsy has become standard practice at children’s hospitals with the appropriate neurosurgical expertise. While the decision to obtain a biopsy should be directed by the presence of atypical radiographic features that call the diagnosis of DIPG into question or the requirement of biopsy tissue for clinical trial enrollment, once this precious tissue is available its use for research should be considered. The majority of DIPG and diffuse midline glioma, H3 K27M-mutant (DMG) models are autopsy-derived or genetically-engineered, each of which has limitations for translational studies, so the use of biopsy tissue for laboratory model development provides an opportunity to create unique model systems. Here, we present a detailed laboratory protocol for the generation of treatment-naïve biopsy-derived DIPG/DMG models.

A Protocol for the Generation of Treatment-naïve Biopsy-derived Diffuse Intrinsic Pontine Glioma and Diffuse Midline Glioma Models

Diffuse intrinsic pontine glioma (DIPG) is a universally fatal tumor of the brainstem, most commonly affecting young children. Due to its location, surgical resection is not achievable, but consideration of a biopsy has become standard practice at children's hospitals with the appropriate neurosurgical expertise. While the decision to obtain a biopsy should be directed by the presence of atypical radiographic features that call the diagnosis of DIPG into question or the requirement of biopsy tissue for clinical trial enrollment, once this precious tissue is available its use for research should be considered. The majority of DIPG and diffuse midline glioma, H3 K27M-mutant (DMG) models are autopsy-derived or genetically-engineered, each of which has limitations for translational studies, so the use of biopsy tissue for laboratory model development provides an opportunity to create unique model systems. Here, we present a detailed laboratory protocol for the generation of treatment-naïve biopsy-derived DIPG/DMG models.

SERUM SODIUM, POTASSIUM AND CHLORIDE AFTER SUPRARENALECTOMY IN CATS WITH DIABETES INSIPIDUS

The external symptoms of suprarenal insufficiency in cats with diabetes insipidus are the same as in those animals with only the suprarenals removed, except that the symptoms develop more rapidly in the former. The serum electrolyte changes, however, are different; there is no consistent or marked decrease in the concentration of sodium or chloride following suprarenalectomy in cats with diabetes insipidus, but there is the usual increase in the concentration of potassium. It is suggested that this indicates that changes in sodium are less characteristic of suprarenal insufficiency than are disturbances of potassium metabolism or distribution. A possible inter-relationship between the suprarenal cortex and the posterior lobe of the pituitary as salt-regulating mechanisms is discussed.

Diagnostic considerations in intra-amniotic syphilis

Amniotic fluid is rarely used in the evaluation of syphilis during pregnancy but was available from a woman with positive serologic tests in the 30th week of gestation. Nonmotile intra-amniotic spirochetes were seen by dark-field microscopy 20 hr after treatment with benzathine penicillin G. The identity of the organism in amniotic fluid was confirmed by immunofluorescent staining. Less than 0.5 units/ml of penicillin was present in the amniotic fluid at this time. The amniotic fluid was positive in the Venereal Disease Research Laboratory (VDRL; Atlanta, GA) test, and the concentration of IgM was elevated as was the ratio of lecithin to sphyngomyelin. Phosphatidyl inositol and phosphatidyl glycerol were also present in the amniotic fluid. After treatment the lecithin-sphyngomyelin ratio declined; phosphatidyl glycerol disappeared, whereas phosphatidyl inositol was still present. Despite evidence of intrauterine growth retardation at 30 weeks, the infant born at 37 weeks was of normal weight and length; however, the head circumference was below the tenth percentile. These studies suggest that analysis of amniotic fluid may provide new insights into the biology of syphilis in pregnancy, but does not constitute a recommendation for routine examination of the amniotic fluid in mothers with reactive serologic tests for syphilis.

Intravenous acyclovir for the treatment of primary genital herpes

Thirty-one patients with first episodes of genital herpes were randomized in a double-blind fashion to intravenous treatment with saline placebo or acyclovir, 5 mg/kg body weight at 8-hour intervals, for 5 days. The median duration of viral shedding from genital lesions after the onset of therapy was significantly shorter for patients given acyclovir (2 days) than for those given placebo (13 days), p less than 0.001. Viral shedding from the pharynx, cervix, urethra, and urine were also shorter in acyclovir-treated patients. (p less than or equal to 0.01 for each comparison). Local and systemic symptoms were shortened by a mean of 5 days and healing of genital lesions by a mean of 12 days in acyclovir-treated patients. (p less than 0.01). Complications during treatment, such as extragenital lesions or urinary retention requiring catheterization, developed in four patients given placebo and in none given acyclovir. (p less than 0.05). Intravenous acyclovir substantially decreases the symptoms, duration of lesions, and complications of primary genital herpes.

Double-blind controlled trial of topical acyclovir in genital herpes simplex virus infections

Sixty-nine patients with first episodes and 111 with recurrent episodes of genital herpes simplex virus (HSV) infection were enrolled in a double-blind trial comparing a 5 percent topical acyclovir ointment versus placebo, polyethylene glycol (PEG). Among acyclovir recipients with first episodes of genital herpes, the mean duration of viral shedding from genital lesions, 2.0 days, mean duration of local pain or itching, 3.6 days, and mean time to healing of lesions, 11.2 days, were less than in placebo recipients 4.6, 6.7, and 15.8 days, respectively (p less than 0.05 for each comparison). Among patients with recurrent genital herpes, the mean duration of viral shedding from genital lesions was 0.8 days in acyclovir recipients compared with 1.7 days in placebo recipients (p less than 0.001). Among men with recurrent genital herpes, the mean time to crusting and healing of lesions was 3.5 and 7.5 days in acyclovir recipients compared with 5.0 and 9.7 days in placebo recipients, p = 0.03 and 0.07, respectively. No significant differences in the duration of symptoms or healing times were noted between acyclovir- and placebo-treated women with recurrent genital herpes. Acyclovir therapy was not associated with a decrease in frequency of clinical recurrences or an increase in the time of the next recurrence in patients with either first or recurrent genital herpes. Topical acyclovir appears effective in shortening some of the clinical manifestations of genital HSV infections.

Multiple sites on prostaglandin cyclooxygenase are determinants in the action of nonsteroidal antiinflammatory agents

Evidence is presented to show that nonsteroidal antiinflammatory drugs react with two sites on the cyclooxygenase (8,11,14-eicosatrienoate, hydrogen-donor:oxygen oxidoreductase, EC 1.14.99.1). Although the degree of interaction with the catalytic site determines the potency of such compounds, interaction with the supplementary site is also obligatory for efficacy as cyclooxygenase inhibitors and may explain the selectivity of such drugs in inhibiting the cyclooxygenase but not the lipoxygenase pathway. Drugs that interact more effectively with the supplementary site than with the catalytic site--i.e., those of weak to moderate activity as cyclooxygenase inhibitors--are shown to prevent inhibition of the enzyme by indomethacin. Compounds in this class are also capable of blocking the ulcerogenic action of indomethacin, which suggests that this antiulcerogenic property stems from a direct action at the level of the cyclooxygenase in the stomach.

Analgesic activity of diflunisal [MK-647; 5-(2,4-difluorophenyl)salicylic acid] in rats with hyperalgesia induced by Freund's adjuvant

A method is described for testing analgesia for narcotic or nonnarcotic drugs in rats injected with Freund's adjuvant in the tail, by manipulation of the tail the day after injection, or of the feet after the development of adjuvant arthritis. The method is responsive to a behavioral depressant or an anti-inflammatory steroid. Diflunisal (MK-647; 5-(2,4-difluorophenyl)salicylic acid] exhibited activity in this assay after oral administration with potency about 25 times greater than that of aspirin, about 3 times that of glafenine and twice that of zomepirac. The onset of activity was within a 1/2 hour for narcotic analgesics but required about an hour for non-narcotic compounds. With the latter, the peak of activity was not attained until 2 to 4 hr, depending on the compound. The peak for diflunisal was delayed until the 3rd or 4th hour, but the onset of action was more prompt and the duration greater as the dose was increased. [14C]Diflunisal was concentrated to some extent in the inflamed tissue after adjuvant injection. Peak levels both in plasma and tissue appeared about 2 hr before peak analgesic effect. Repeated administration of large doses produced neither tolerance nor sensitization to the analgesic action of diflunisal. Naloxone and naltrexone did not antagonize the action of the compound, but when morphine and diflunisal were given together, the overall effect was enhanced.