Compact Bidirectional Promoters for Dual-Gene Expression in a Sleeping Beauty Transposon.

Promoter choice is an essential consideration for transgene expression in gene therapy. The expression of multiple genes requires ribosomal entry or skip sites, or the use of multiple promoters. Promoter systems comprised of two separate, divergent promoters may significantly increase the size of genetic cassettes intended for use in gene therapy. However, an alternative approach is to use a single, compact, bidirectional promoter. We identified strong and stable bidirectional activity of the RPBSA synthetic promoter comprised of a fragment of the human Rpl13a promoter, together with additional intron/exon structures. The Rpl13a-based promoter drove long-term bidirectional activity of fluorescent proteins. Similar results were obtained for the EF1-α and LMP2/TAP1 promoters. However, in a lentiviral vector, the divergent bidirectional systems failed to produce sufficient titres to translate into an expression system for dual chimeric antigen receptor (CAR) expression. Although bidirectional promoters show excellent applicability to drive short RNA in Sleeping Beauty transposon systems, their possible use in the lentiviral applications requiring longer and more complex RNA, such as dual-CAR cassettes, is limited.

An Extremely Rare Case of Prostate and Bladder Wall Involvement of Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults and is characterized by monoclonal proliferation of B-cell lymphocytes which are morphologically mature, but immunologically dysfunctional. The primary sites of disease involvement include peripheral blood, lymph nodes, spleen, and bone marrow. CLL can also present locally and aggressively at extranodal sites. We describe the case of a 74-year-old gentleman with multiple medical comorbidities who was Foley catheter-dependent at baseline for bladder outlet obstruction. He was detected to have Rai stage I CLL following an inguinal lymph node biopsy and was on regular outpatient surveillance. Later, he underwent a prostate biopsy for evaluation of hematuria, results of which were consistent with CLL involvement in the prostate and urinary bladder. The patient was started on single-agent ibrutinib, and demonstrated an excellent clinical response to bladder outlet obstruction. His long-term Foley catheter was discontinued within 5 days of ibrutinib therapy. Unfortunately, 1 year later, he had disease progression, and therapy was changed to a single-agent rituximab, to which he is responding well. Our case is unique as it brings up the first reported case of prostate and bladder wall CLL.

Pembrolizumab-Induced Acute Skin Reaction: A Case Report and Review of Literature.

The development of immune checkpoint inhibitors is considered to be one of the most important advances in cancer treatment. Pembrolizumab is an immune checkpoint inhibitor against programmed death-ligand 1 (PD-L1) receptor that has demonstrated antineoplastic activity against various malignancies including non-small cell lung cancer, melanoma, and triple-negative breast cancer. Pembrolizumab has been associated with significant dermatological adverse reactions, referred to as immune-related adverse events. The cutaneous adverse effects can affect the quality of life of the patient and can result in dose reduction or even discontinuation of the treatment. Hence it is of utmost importance to have a comprehensive understanding of the cutaneous toxicities for prompt initiation of treatment. We present the case of a 49-year-old male with metastatic non-small cell lung cancer (NSCLC) with 100% PD-L1 expression, who suffered a severe cutaneous reaction involving more than 95% of body surface area, following the first dose of pembrolizumab. He was treated with low-dose systemic steroids (prednisone 10 mg), to which he responded well. Since the patient showed excellent symptomatic and clinical response to pembrolizumab, it was not discontinued. The patient has not developed a rash with subsequent doses of pembrolizumab, and the steroids were tapered off.

Anti-Apoptotic c-FLIP Reduces the Anti-Tumour Activity of Chimeric Antigen Receptor T Cells.

CAR T cell treatment of solid tumours is limited by poor persistence partly due to CD95 ligand (CD95L)-induced apoptosis. Both T cells and cells within the tumour microenvironment (TME) may express CD95L, triggering apoptosis in CD95-receptor-positive CAR T cells. Tonic signalling of CAR T cells may also increase CD95-dependent AICD. Because the intracellular protein c-FLIP protects T cells from AICD, we expressed c-FLIPp43 within a Her-2 targeted CAR cassette and evaluated the potential of c-FLIPp43 through in vitro functional assays and in vivo tumour-bearing xenograft model. cFLIP expression protected against CD95L-induced cell death in the Jurkat T cell lines. However, in primary human CAR T cells containing CAR-CD28 domains, c-FLIPp43 overexpression had minimal additional impact on resistance to CD95L-induded cell death. In vitro cytotoxicity against a breast cancer tumour cell line was not altered by c-FLIPp43 expression, but the expression of c-FLIPp43 in Her2-CAR T cells lowered interferon-γ secretion, without markedly affecting IL-2 levels, and c-FLIPp43-Her2-CAR T cells showed reduced anti-tumour activity in immunodeficient mice with breast cancer. The findings of this study provide a new understanding of the effects of controlling extrinsic apoptosis pathway suppression in CAR T cells, suggesting that c-FLIPp43 expression reduces anti-tumour immunity through the modulation of effector T cell pathways.

Optimisation of Tet-On inducible systems for Sleeping Beauty-based chimeric antigen receptor (CAR) applications.

Regulated expression of genetic elements that either encode polypeptides or various types of functional RNA is a fundamental goal for gene therapy. Inducible expression may be preferred over constitutive promoters to allow clinician-based control of gene expression. Existing Tet-On systems represent one of the tightest rheostats for control of gene expression in mammals. However, basal expression in absence of tetracycline compromises the widespread application of Tet-controlled systems in gene therapy. We demonstrate that the order of P2A-linked genes of interest was critical for maximal response and tightness of a chimeric antigen receptor (CAR)-based construct. The introduction of G72V mutation in the activation region of the TetR component of the rtTA further improved the fold response. Although the G72V mutation resulted in a removal of a cryptic splice site within rtTA, additional removal of this splice site led to only a modest improvement in the fold-response. Selective removal of key promoter elements (namely the BRE, TATA box, DPE and the four predicted Inr) confirmed the suitability of the minimal CMV promoter and its downstream sequences for supporting inducible expression. The results demonstrate marked improvement of the rtTA based Tet-On system in Sleeping Beauty for applications such as CAR T cell therapy.

Promoter choice: Who should drive the CAR in T cells?

Chimeric antigen receptor (CAR) T cell therapy is an effective treatment for B cell malignancies, with emerging potential for the treatment of other hematologic cancers and solid tumors. The strength of the promoter within the CAR cassette will alter CAR-polypeptide levels on the cell surface of the T cell-impacting on the kinetics of activation, survival and memory cell formation in T cells. In addition to the CAR, promoters can be used to drive other genes of interest to enhance CAR T cell function. Expressing multiple genes from a single RNA transcript can be effectively achieved by linking the genes via a ribosomal skip site. However, promoters may differ in their ability to transcribe longer RNAs, or could interfere with lentiviral production, or transduction frequencies. In this study we compared the ability of the strong well-characterized promoters CMV, EF-1, hPGK and RPBSA to drive functional expression of a single RNA encoding three products: GFP, CAR, plus an additional cell-survival gene, Mcl-1. Although the four promoters produced similarly high lentiviral titres, EF-1 gave the best transduction efficacy of primary T cells. Major differences were found in the ability of the promoters to drive expression of long RNA encoding GFP, CAR and Mcl-1, highlighting promoter choice as an important consideration for gene therapy applications requiring the expression of long and complex mRNA.

Regulation of human Mcl-1 by a divergently-expressed antisense transcript.

Mcl-1 is a member of the Bcl-2 anti-apoptotic protein family with important roles in the development, lifespan and metabolism of lymphocytes, as well as oncogenesis. Mcl-1 displays the shortest half-life of all Bcl-2 family members, with miRNA interference and proteasomal degradation being major pathways for Mcl-1 downregulation. In this study, we have identified a previously undescribed control mechanism active at the RNA level. A divergently transcribed lncRNA LOC107985203 (named here mcl1-AS1) negatively modulated Mcl-1 expression resulting in downregulation of Mcl-1 at both mRNA and protein level in a time-dependent manner. Using reporter assays, we confirmed that the mcl1-AS1 lncRNA promoter was located within Mcl-1 coding region. We next placed mcl1-AS1 under tetracycline-inducible control and demonstrated decreased viability in HEK293 cells upon doxycycline induction. Inhibition of mcl1-AS1 with shRNA reversed drug sensitivity. Bioinformatics surveys predicted direct mcl1-AS1 lncRNA binding to Mcl-1 transcripts, suggesting its mechanism in Mcl-1 expression is at the transcriptional level, consistent with a common role for anti-sense transcripts. The identification of a bi-directional promoter and lncRNA controlling Mcl-1 expression will have implications for controlling Mcl-1 activity in cancer cells, or for the purpose of enhancing the lifespan and quality of anti-cancer T lymphocytes.

Differential expression of miRNAs in acute myeloid leukemia quantified by Nextgen sequencing of whole blood samples.

New approaches are needed for understanding and treating acute myeloid leukemia (AML). MicroRNAs (miRs) are important regulators of gene expression in all cells and disruption of their normal expression can lead to changes in phenotype of a cell, in particular the emergence of a leukemic clone. We collected peripheral blood samples from 10 adult patients with newly diagnosed AML, prior to induction chemotherapy, and 9 controls. Two and a half ml of whole blood was collected in Paxgene RNA tubes. MiRNA was purified using RNeasy mini column (Qiagen). We sequenced approximately 1000 miRs from each of 10 AML patients and 9 controls. In subset analysis, patients with NPM1 and FLT3 mutations showed the greatest number of miRNAs (63) with expression levels that differed from control with adjusted p-value of 0.05 or less. Some of these miRs have been described previously in association with leukemia, but many are new. Our approach of global sequencing of miRs as opposed to microarray analysis removes the bias regarding which miRs to assay and has demonstrated discovery of new associations of miRs with AML. Another strength of our approach is that sequencing miRs is specific for the 5p or 3p strand of the gene, greatly narrowing the proposed target genes to study further. Our study provides new information about the molecular changes that lead to evolution of the leukemic clone and offers new possibilities for monitoring relapse and developing new treatment strategies.

Epidermal growth factor receptor T790M mutation-positive metastatic non-small-cell lung cancer: focus on osimertinib (AZD9291).

Adenocarcinoma is the most common type of non-small-cell lung cancer (NSCLC). Adenocarcinoma with epidermal growth factor receptor (EGFR) mutations accounts for 8%-30% of all cases of NSCLC depending on the geography and ethnicity. EGFR-mutated NSCLC usually responds to first-line therapy with EGFR tyrosine kinase inhibitors (TKIs). However, there is eventual loss of efficacy to TKIs due to development of resistance. The most frequent cause for resistance is a second EGFR mutation in exon 20 (T790M), which is encountered in up to 62% of patients. Osimertinib is one of the third-generation EGFR TKIs with a high selective potency against T790M mutants. In Phase I trial of osimertinib in advanced lung cancer after progression on EGFR TKIs, the response rate and disease control rate were 61% and 95%, respectively. A subsequent Phase II (AURA2) trial demonstrated a disease control rate of 92%, a response rate of 71%, a median duration of response of 7.8 months, and a median progression-free survival of 8.6 months. Osimertinib was approved by the US Food & Drug Administration in November 2015 for patients whose tumors exhibited T790M mutation and for those with progressive disease on other EGFR TKIs. In this review, we address the role of EGFR TKIs in the management of EGFR mutation lung cancer and the mechanisms of resistance to TKIs with a focus on the role of osimertinib. Data from completed trials of osimertinib, ongoing trials, as well as novel diagnostic methods to detect EGFR T790M mutation are reviewed.

Navigating the Challenges of Adjuvant Chemotherapy in Older Patients with Early-Stage Non-Small-Cell Lung Cancer.

Lung cancer is a disease of older adults. In the US and worldwide, more than 60% of patients being diagnosed are over the age of 65 years. The preferred treatment of stage I-II non-small-cell lung cancer (NSCLC) is surgical resection. Adjuvant chemotherapy with a platinum-based combination is the standard of care for patients with early-stage NSCLC after surgery. However, there have been no large prospective studies to test the efficacy of adjuvant chemotherapy in the elderly, the population most affected by lung cancer. The available evidence is limited to retrospective reviews of large population databases or post hoc analyses of prospective studies in age-unselected populations. This review aims to address the knowledge gap pertaining to the use of adjuvant chemotherapy in older patients with resected NSCLC. There are many barriers to use of adjuvant chemotherapy in older adults with NSCLC. The utilization of adjuvant chemotherapy amongst older adults has been slow but is improving. While the elderly may tolerate a lower dose intensity of chemotherapy compared with younger patients, they do garner benefit from adjuvant chemotherapy. There is a lack of a standardized tool to risk-stratify older patients for adjuvant chemotherapy after resection. Geriatric assessment may help guide decision making in the clinical practice setting. The principles of geriatric assessment and commonly employed tools for such assessment will be reviewed. Further, the emerging therapies in adjuvant treatment of lung cancer based on genetic mutations will be discussed.