p53-based strategy to reduce hematological toxicity of chemotherapy: A proof of principle study

Identification of the natural chalcone glycoside hydroxysafflor yellow A as a suppressor of P53 overactivation-associated hematopoietic defects

Enhanced P53 signaling may lead to hematopoietic disorders, yet an effective therapeutic strategy is still lacking. Our study, along with previous research, suggests that P53 overactivation and hematopoietic defects are major consequences of zinc deficiency. However, the relationship between these two pathological processes remains unclear. In this study, we observed a severe reduction in the number of hematopoietic stem cells (HSCs) and multi-lineage progenitor cells in zebrafish treated with the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine and showed the indispensable role of P53 signaling in the process. Next, we took advantage of HSCs-labeled transgenic zebrafish and conducted a highly efficient phenotypic screening for small molecules against P53-dependent hematopoietic disorders. Hydroxysafflor yellow A (HSYA), a natural chalcone glycoside, exhibited potent protection against hematopoietic failure in zinc-deficient zebrafish and strongly inhibited the P53 pathway. We confirmed the protective effect of HSYA in zinc-deficient mice bone marrow nucleated cells, which showed a significant suppression of P53 signaling and oxidative stress. Furthermore, the hematopoietic-protective activity of HSYA was validated using a mice model of myelotoxicity induced by 5-FU. In summary, our work provides an effective phenotypic screening strategy for identifying hematopoietic-protective agents and reveals the novel role of HSYA as a promising lead compound in rescuing hematopoietic disorders associated with P53 overactivation.

Low-Cost Genetic and Clinical Predictors of Response and Toxicity of Platinum-Based Chemotherapy in Advanced Non-Small Cell Lung Cancer

Background

This study aimed to evaluate for the first time whether certain genetic and clinical factors could serve as minimally invasive predictors of survival and toxicity to platinum-based chemotherapy in advanced lung adenocarcinoma.

Methods

The study included 121 advanced lung adenocarcinoma patients treated with platinum-based dublets until progression or unacceptable toxicity. Response was evaluated using standard radiological methods and toxicity graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Genotyping was performed using PCR-RFLP. Statistical significance was set at P < .05.

Results

No significant influence of the examined polymorphisms on the occurrence of high-grade toxicity was detected. However, TP53 72Pro allele carriers were more prone to nausea (P = .037) and thrombocytopenia (P = .051). Anemia and neuropathy occurred more frequently in XRCC1 399Arg allele carriers (Pearson χ2 test, P = .025 and P = .004 respectively). RAD51 135CC carriers were significantly more prone to neutropenia (P = .027).

Conclusions

A set of easily determined genetic and clinical predictors of survival and specific toxicity profiles of platinum-based chemotherapy in advanced lung adenocarcinoma were determined in this study, which might be useful for the construction of population-specific, time- and cost-efficient prognostic and predictive algorithms.

Initial report of a phase II study with R-FND followed by ibritumomab tiuxetan radioimmunotherapy and rituximab maintenance in patients with untreated high-risk follicular lymphoma

R-FND (rituximab, fludarabine, mitoxantrone, and dexamethasone) can induce molecular remissions in indolent lymphoma. The addition of ⁹⁰yttrium ibritumomab tiuxetan (⁹⁰YIT) radioimmunotherapy following first-line induction treatment in patients with advanced follicular lymphoma (FL) may improve remission rates. We now report 10-year follow-up results from our sequential treatment approach with an abbreviated regimen of R-FND followed by ⁹⁰YIT consolidation and rituximab maintenance. Forty-nine patients were enrolled; 47 received treatment. Patients had high-risk (FLIPI score ≥3) FL of grade 1-3A and stage III/IV with adequate hematologic function. Following R-FND, the complete and partial response rates were 91% and 8.5%, respectively. After ⁹⁰YIT consolidation, the CR rate increased to 97%. The 10-year PFS rate was 49%. The most common non-hematologic, grade 3 or 4 adverse events were fatigue, dyspnea, and myalgia. Five developed myelodysplastic syndrome (MDS). This treatment approach is most appropriate in FLIPI-based high-risk patients whose outlook with standard therapy is inadequate.

Status quo of p53 in the treatment of tumors

The p53 gene is pivotal for oncogenesis in a combination of mutations in oncogenes and antioncogenes. The ubiquitous loss of the p53 pathway in human cancers has generated considerable interest in developing p53-targeted cancer therapies, but current ideas and approaches targeting p53 are conflicting. Current researches focus on cancer-selective drugs with therapeutic strategies that both activate and inhibit p53. As p53 is ubiquitously lost in human cancers, the strategy of exogenous p53 addition is reasonable. However, p53 acts not equally in all cell types; thus, individualized p53 therapy is the direction of future research. To clarify the controversies on p53 for improvement of future antitumor studies, the review focuses on the available technological protocols, including their advantages and limitations in terms of future therapeutic use of p53 in the management of tumors.

Regulation of the Mdm2-p53 signaling axis in the DNA damage response and tumorigenesis

The p53 tumor suppressor acts as a guardian of the genome in mammalian cells undergoing DNA double strand breaks induced by a various forms of cell stress, including inappropriate growth signals or ionizing radiation. Following damage, p53 protein levels become greatly elevated in cells and p53 functions primarily as a transcription factor to regulate the expression a wide variety of genes that coordinate this DNA damage response. In cells undergoing high amounts of DNA damage, p53 can promote apoptosis, whereas in cells undergoing less damage, p53 promotes senescence or transient cell growth arrest and the expression of genes involved in DNA repair, depending upon the cell type and level of damage. Failure of the damaged cell to undergo growth arrest or apoptosis, or to respond to the DNA damage by other p53-coordinated mechanisms, can lead to inappropriate cell growth and tumorigenesis. In cells that have successfully responded to genetic damage, the amount of p53 present in the cell must return to basal levels in order for the cell to resume normal growth and function. Although regulation of p53 levels and function is coordinated by many proteins, it is now widely accepted that the master regulator of p53 is Mdm2. In this review, we discuss the role(s) of p53 in the DNA damage response and in tumor suppression, and how post-translational modification of Mdm2 regulates the Mdm2-p53 signaling axis to govern p53 activities in the cell.

An extra copy of p53 suppresses development of spontaneous Kras-driven but not radiation-induced cancer

The tumor suppressor p53 blocks tumor progression in multiple tumor types. Radiation-induced cancer following exposure to radiation therapy or space travel may also be regulated by p53 because p53 has been proposed to respond to DNA damage to suppress tumorigenesis. Here, we investigate the role of p53 in lung carcinogenesis and lymphomagenesis in LA-1 Kras^G12D mice with wild-type p53 or an extra copy of p53 (super p53) exposed to fractionated total body irradiation with low linear energy transfer (low-LET) X-rays or high-LET iron ions and compared tumor formation in these mice with unirradiated controls. We found that an additional copy of p53 suppressed both Kras-driven lung tumor and lymphoma development in the absence of radiation. However, an additional copy of p53 did not affect lymphoma development following low- or high-LET radiation exposure and was unable to suppress radiation-induced expansion of thymocytes with mutated Kras. Moreover, radiation exposure increased lung tumor size in super p53 but not wild-type p53 mice. These results demonstrate that although p53 suppresses the development of spontaneous tumors expressing Kras^G12D, in the context of exposure to ionizing radiation, an extra copy of p53 does not protect against radiation-induced lymphoma and may promote Kras^G12D mutant lung cancer.

Emerging agents for the prevention of treatment induced neutropenia in adult cancer patients

INTRODUCTION

The administration of myeloid growth factors is the only approved treatment for the prevention of chemotherapy induced neutropenia and febrile neutropenia. However, their specific indications and contraindications and potential side effects limit their application to only a relatively small subset of patients at the highest risk for complications, such as infection.

AREAS COVERED

A computerized systematic literature search was performed through Medline, Google Scholar, Cochrane Library, the Pharmaprojects database and the clinicaltrials.gov website. The shortcomings of the existing treatment approach are reviewed, along with a synopsis of the characteristics of novel agents that protect bone marrow progenitors from the cytotoxic effects of antineoplastic treatment that may be used in the future as a stand-alone preventive strategy or as an adjunct to growth factors.

EXPERT OPINION

There is an abundance of agents undergoing evaluation for the prevention of treatment-induced neutropenia. The appropriate selection of patients, the optimization of the use of existing agents and the increasing competition from biosimilars which likely ensure future decreases in healthcare costs are essential for growth factors to retain their dominant position in this setting.

p53-based strategy to reduce hematological toxicity of chemotherapy: A proof of principle study

p53 activation is a primary mechanism underlying pathological responses to DNA damaging agents such as chemotherapy and radiotherapy. Our recent animal studies showed that low dose arsenic (LDA)-induced transient p53 inhibition selectively protected normal tissues from chemotherapy-induced toxicity. Study objectives were to: 1) define the lowest safe dose of arsenic trioxide that transiently blocks p53 activation in patients and 2) assess the potential of LDA to decrease hematological toxicity from chemotherapy. Patients scheduled to receive minimum 4 cycles of myelosuppressive chemotherapy were eligible. For objective 1, dose escalation of LDA started at 0.005 mg/kg/day for 3 days. This dose satisfied objective 1 and was administered before chemotherapy cycles 2, 4, and 6 for objective 2. p53 level in peripheral lymphocytes was measured on day 1 of each cycle by ELISA assay. Chemotherapy cycles 1, 3, and 5 served as the baseline for the subsequent cycles of 2, 4, and 6 respectively. If p53 level for the subsequent cycle was lower (or higher) than the baseline cycle, p53 was defined as "suppressed" (or "activated") for the pair of cycles. Repeated measures linear models of CBC in terms of day, cycle, p53 activity and interaction terms were used. Twenty-six patients treated with 3 week cycle regimens form the base of analyses. The mean white blood cell, hemoglobin and absolute neutrophil counts were significantly higher in the "suppressed" relative to the "activated" group. These data support the proof of principle that suppression of p53 could lead to protection of bone marrow in patients receiving chemotherapy. This trial is registered in ClinicalTrials.gov. Identifier: NCT01428128.