PTEN and DNA-PK determine sensitivity and recovery in response to WEE1 inhibition in human breast cancer

Inhibition of WEE1 kinase by AZD1775 has shown promising results in clinical cancer trials, but markers predicting AZD1775 response are lacking. Here we analysed AZD1775 response in a panel of human breast cancer (BC) cell lines by global proteome/transcriptome profiling and identified two groups of basal-like BC (BLBCs): ‘PTEN low’ BLBCs were highly sensitive to AZD1775 and failed to recover following removal of AZD1775, while ‘PTEN high’ BLBCs recovered. AZD1775 induced phosphorylation of DNA-PK, protecting cells from replication-associated DNA damage and promoting cellular recovery. Deletion of DNA-PK or PTEN, or inhibition of DNA-PK sensitized recovering BLBCs to AZD1775 by abrogating replication arrest, allowing replication despite DNA damage. This was linked to reduced CHK1 activation, increased cyclin E levels and apoptosis. In conclusion, we identified PTEN and DNA-PK as essential regulators of replication checkpoint arrest in response to AZD1775 and defined PTEN as a promising biomarker for efficient WEE1 cancer therapy.

ABL2 suppresses FLT3-ITD-induced cell proliferation through negative regulation of AKT signaling

The type III receptor tyrosine kinase FLT3 is one of the most commonly mutated oncogenes in acute myeloid leukemia (AML). Inhibition of mutated FLT3 in combination with chemotherapy has displayed promising results in clinical trials. However, one of the major obstacles in targeting FLT3 is the development of resistant disease due to secondary mutations in FLT3 that lead to relapse. FLT3 and its oncogenic mutants signal through associating proteins that activate downstream signaling. Thus, targeting proteins that interact with FLT3 and their downstream signaling cascades can be an alternative approach to treat FLT3-dependent AML. We used an SH2 domain array screen to identify novel FLT3 interacting proteins and identified ABL2 as a potent interacting partner of FLT3. To understand the role of ABL2 in FLT3-mediated biological and cellular events, we used the murine pro-B cell line Ba/F3 as a model system. Overexpression of ABL2 in Ba/F3 cells expressing an oncogenic mutant of FLT3 (FLT3-ITD) resulted in partial inhibition of FLT3-ITD-dependent cell proliferation and colony formation. ABL2 expression did not alter the kinase activity of FLT3, its ubiquitination or its stability. However, it partially blocked FLT3-induced AKT phosphorylation without affecting ERK1/2 and p38 activation. Taken together our data suggest that ABL2 acts as negative regulator of signaling downstream of FLT3.

Abstract 325: Pediatric relapsed acute lymphoblastic leukemia patients display enrichment of the PI3K/mTOR pathway and respond to the dual PI3K/mTOR inhibitor PKI-587

Although significant improvements have been observed in the treatment of acute lymphoblastic leukemia, there is a substantial subset of high-risk T-ALL patients with relatively poor prognosis. T-cell acute lymphoblastic leukemia (T-All) is a hematopoietic malignancy affecting lymphoblast of T-cell lineage which cause lots of hematopoietic cancer related deaths every year all over the world. The current overall cure rates of newly diagnosed childhood ALL are more than 80% in Europe, but approximately 20% of patients relapse due to treatment failure in childhood ALL. Like other leukemia types, alterations of PI3K/mTOR pathway are predominant in T-ALL which is also responsible for treatment failure and relapse. In this study, two different gene expression data sets of relapsed patients also displayed enrichment of the PI3K/mTOR pathway. Out of 88 different inhibitors targeting multiple components of this pathway, we observed that PKI-587 was the most selective to the T-ALL cell line CCRF-CEM. Thus, we characterized the activity of the novel dual PI3K/mTOR pathway inhibitor PKI-587 using CCRF-CEM and Molt3 cells. We observed that PKI-587 blocked proliferation, colony formation and induced apoptosis in the T-ALL cell lines and selectively abrogated PI3K/mTOR without affecting the MAPK signaling. In vivo PI3K/mTOR inhibition delayed tumor progression, and reduced tumor load in a NSG/SCID xenograft mouse model. Since no deceptive body weight decrease was noticed, our conclusion is that this dose is effective and well tolerated. The beneficial effects of PKI-587 on T-ALL cells that has been observed in this study both in vitro and in vivo warrant further investigation.

Citation Format: Mohiuddin Gazi, Sausan A. Moharram, Alissa Marhäll, Kinjal Shah, Julhash U. Kazi. Pediatric relapsed acute lymphoblastic leukemia patients display enrichment of the PI3K/mTOR pathway and respond to the dual PI3K/mTOR inhibitor PKI-587 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 325. doi:10.1158/1538-7445.AM2017-325

Tyrosine 842 in the activation loop is required for full transformation by the oncogenic mutant FLT3-ITD

The type III receptor tyrosine kinase FLT3 is frequently mutated in acute myeloid leukemia. Oncogenic FLT3 mutants display constitutive activity leading to aberrant cell proliferation and survival. Phosphorylation on several critical tyrosine residues is known to be essential for FLT3 signaling. Among these tyrosine residues, Y842 is located in the so-called activation loop. The position of this tyrosine residue is well conserved in all receptor tyrosine kinases. It has been reported that phosphorylation of the activation loop tyrosine is critical for catalytic activity for some but not all receptor tyrosine kinases. The role of Y842 residue in FLT3 signaling has not yet been studied. In this report, we show that Y842 is not important for FLT3 activation or ubiquitination but plays a critical role in regulating signaling downstream of the receptor as well as controlling receptor stability. We found that mutation of Y842 in the FLT3-ITD oncogenic mutant background reduced cell viability and increased apoptosis. Furthermore, the introduction of the Y842 mutation in the FLT3-ITD background led to a dramatic reduction in in vitro colony forming capacity. Additionally, mice injected with cells expressing FLT3-ITD/Y842F displayed a significant delay in tumor formation, compared to FLT3-ITD expressing cells. Microarray analysis comparing gene expression regulated by FLT3-ITD versus FLT3-ITD/Y842F demonstrated that mutation of Y842 causes suppression of anti-apoptotic genes. Furthermore, we showed that cells expressing FLT3-ITD/Y842F display impaired activity of the RAS/ERK pathway due to reduced interaction between FLT3 and SHP2 leading to reduced SHP2 activation. Thus, we suggest that Y842 is critical for FLT3-mediated RAS/ERK signaling and cellular transformation.

The complete mitochondrial genome sequence of Oncicola luehei (Acanthocephala: Archiacanthocephala) and its phylogenetic position within Syndermata

In the present study, we determined the complete mitochondrial genome sequence of Oncicola luehei (14,281bp), the first archiacanthocephalan representative and the second complete sequence from the phylum Acanthocephala. The complete genome contains 36 genes including 12 protein coding genes, 22 transfer RNA (tRNA) genes and 2 ribosomal RNA genes (rrnL and rrnS) as reported for other syndermatan species. All genes are encoded on the same strand. The overall nucleotide composition of O. luehei mtDNA is 37.7% T, 29.6% G, 22.5% A, and 10.2% C. The overall A+T content (60.2%) is much lower, compared to other syndermatan species reported so far, due to the high frequency (18.3%) of valine encoded by GTN in its protein-coding genes. Results from phylogenetic analyses of amino acid sequences for 10 protein-coding genes from 41 representatives of major metazoan groups including O. luehei supported monophyly of the phylum Acanthocephala and of the clade Syndermata (Acanthocephala+Rotifera), and the paraphyly of the clade Eurotatoria (classes Bdelloidea+Monogononta from phylum Rotifera). Considering the position of the acanthocephalan species within Syndermata, it is inferred that obligatory parasitism characteristic of acanthocephalans was acquired after the common ancestor of acanthocephalans diverged from its sister group, Bdelloidea. Additional comparison of complete mtDNA sequences from unsampled acanthocephalan lineages, especially classes Polyacanthocephala and Eoacanthocephala, is required to test if mtDNA provides reliable information for the evolutionary relationships and pattern of life history diversification found in the syndermatan groups.

Utility of biofeedback for the daytime syndrome of urinary frequency and urgency of childhood

OBJECTIVES

To evaluate in a preliminary study the utility of biofeedback for the treatment of the daytime syndrome of urinary frequency and urgency of childhood, a benign, self-limited condition with symptoms that can last for months or years. Observation is a commonly recommended approach to this syndrome because medications and other forms of therapy are often not effective.

METHODS

During a 2-year period, 89 children (34 boys and 55 girls) presented with this syndrome. Patient age ranged from 4 to 11 years, and duration of symptoms ranged from 1 to 38 months. All children were evaluated with a history, physical examination, urinalysis and culture, and renal and bladder ultrasound scanning. After the evaluation, the parents were offered either observation or surface patch electromyography biofeedback for the problem.

RESULTS

Overall, 84 parents (94.3%) selected biofeedback for their child. After 1 month of biofeedback, 34.5% of children were able to achieve a 2 to 4-hour voiding interval. After 2 to 4 months of biofeedback, another 51.2% of patients experienced the same improvement. Overall, 85.7% of children who underwent biofeedback had symptom improvement. In 14.3% of children, no symptom improvement was noted after 4 months of biofeedback and these children were considered nonresponders.

CONCLUSIONS

The results of this study suggest that biofeedback may be a treatment option for this disorder and warrants further investigation.

[Appendicitis in Niger: current prognosis]

Acute appendicitis remains one of the most frequent emergencies in abdominal surgery. Surgery is usually straightforward and prognosis excellent. However, outcome depends essentially on how soon diagnosis is made. In Niger, the 1990s were marked by the development of private medicine and the deterioration of services in state health structures (health centres and hospitals). The goal of this prospective study, carried out over 24 months (March 1997-March 1999) was to analyse existing appendicitis prognosis in our country. The study population was made up of 362 patients and we based our survey on a number of factors found in the medical literature, and in particular on a similar study conducted in the same hospital in 1989 by another group of surgeons. Delays in diagnosis and thus therapy still today tends to transform prognosis for simple acute appendicitis into that of peritonitis. The numerous and varied post-operative complications keep the mortality rate at 4%.

Oral health care of Saudi leukemic patients

There is a growing demand in Saudi Arabia for better oral health care; however, the need varies from one group to another. Patients with leukemia require more dental care than do healthy subjects because of associated serious oral complications and physical disabilities in maintaining plaque-free teeth. Because of a dental manpower shortage, leukemic patients in Saudi Arabia are likely to be receiving less specialist dental care than they require. A pilot study of 30 leukemic patients from four major hospitals in Riyadh showed high indices of plaque, calculus, and gingival bleeding. While hopitalized, 54% of the patients had a plaque index of greater than 80%, whereas 31% of the patients had a bleeding index of greater than 80%. All leukemic patients examined had either oral ulcerations, fungal infection, gingival enlargement, or gingival bleeding that necessitated further medical attention. This study indicated that Saudi leukemic patients desperately require better oral health care. Additional specialist dental centers staffed by appropriately trained dental personnel are urgently needed to provide oral health care for these patients.

Meswak chewing stick versus conventional toothbrush as an oral hygiene aid

This study consisted of two trials. Trial 1 compared the meswak with the toothbrush when used twice and five times a day. Trial 2 compared habitual meswak users with toothbrush users. Under experimental conditions, a significant reduction in gingivitis was found both buccally (p less than 0.01) and lingually (p less than 0.05) after using a meswak five times a day compared with a conventional toothbrush. Twice a day brushing with a meswak produced a significant reduction in gingivitis buccally (p less than 0.005) compared with toothbrushing, but lingually the difference was insignificant. There were no significant differences in plaque scores between a meswak and a conventional toothbrush when brushing was continued five times a day. Plaque scores became significantly higher when a meswak was used only twice a day compared with toothbrushing, specifically on the lingual surfaces of the teeth (p less than 0.01). Habitual meswak users showed a significant reduction in gingival bleeding (p less than 0.05) and interproximal bone height (p less than 0.02) compared with toothbrush users. The differences in plaque scores and pocket depth measurements between the two groups were insignificant. The results imply that a meswak, used five times a day, may offer a suitable alternative to a toothbrush for reducing plaque and gingivitis. However, meswak may not be sufficient for maintaining interproximal dental health when used without the support of other oral hygiene aids.

More unusual pigmentations of the gingiva

Three unusual types of oral pigmentation are presented. The first is a brown orange pigmentation caused by the habit of using the bark of Juglans regia for teeth cleaning. The second is a bright yellow pigmentation associated with the habit of chewing the seeds of Cola nitida. The third is a generalized mousy brown pigmentation related to the habit of chewing the leaves of Catha edulis. The purpose of this article is to describe the nature of these pigmentations and to present their clinical and histologic features.