No abstract

The human T-cell leukemia virus type I tax, gene product is responsible for the increased expression of several cytokine and cellular genes that contain NF-KB regulatory sequences. Our laboratory has previously demonstrated that purified, extracellular Tax, protein induced the nuclear accumulation of NF-KB binding activity in lymphoid cells. Since HTLV-I infection causes increased levels of lymphotoxin tumor necrosis factor-,8 [TNF-0] and immunoglobulin secretion, we have studied the interaction of NF-KB proteins from Taxl-stimulated cells with the TNF-I and immunoglobulin kappa (IgK) light chain genes. Tax1 induction of NF-KB occurred in the presence of cycloheximide, and Tax1 stimulation did not result in increased levels of NF-KB or c-rel RNA. These results indicate that new synthesis of NF-KB proteins was not required for induction of NF-KB-binding activity. With use of the IgK NF-KB-binding site as a probe, two distinct NF-KB gel shift complexes were induced by the Tax1 protein. A slower-migrating complex, Cl, was inhibited by the addition of purified IKB. In contrast, the faster-migrating C2 complex was not inhibited by IKB, but C2 was increased by detergent treatment of cytoplasmic extracts, suggesting that its binding activity was also regulated by an inhibitor. The Tax,-stimulated proteins that interacted with the NF-KB-binding sites in the IgK and TNF-jB promoters were distinct. A 75-kDa protein preferentially associated with the IgK NF-KB-binding site. In contrast, a 59-kDa protein associated with the TNF-I NF-KB-binding site. Tax1 stimulation led to increased levels of TNF-,I and IgK mRNA, as measured by reverse transcription and polymerase chain reaction analysis. These results represent the first experimental evidence that extracellular Tax1 can regulate the expression of endogenous cellular genes.

Sequences which control basal human T-cell lymphotropic virus type I (HTLV-I) transcription likely play an important role in initiation and maintenance of virus replication. We previously identified and analyzed a 45-nucleotide sequence (downstream regulatory element 1 [DRE 1]), +195 to +240, at the boundary of the RIU5 region of the long terminal repeat which is required for HTLV-I basal transcription. We identified a protein, p37, which specifically bound to DRE 1. An affinity column fraction, containing p37, stimulated HTLV-I transcription approximately 12-fold in vitro. We now report the identification of a cDNA clone (15B-7), from a Jurkat expression library, that binds specifically to the DRE 1 regulatory sequence. Binding of the cDNA fusion protein, similarly to the results obtained with purified Jurkat protein, was decreased by introduction of site-specific mutations in the DRE 1 regulatory sequence. In vitro transcription and translation of 15B-7 cDNA produced a fusion protein which bound specifically to the HTLV-I +195 to +240 oligonucleotide. The partial cDNA encodes a protein which is homologous to the C-terminal 196 amino acids of the 36-kDa transcription factor, YB-1. Cotransfection of a YB-1 expression plasmid increases HTLV-I basal transcription approximately 14-fold in Jurkat T lymphocytes. On the basis of the molecular weight, DNA-binding characteristics, and in vivo transactivation activity, we suggest that the previously identified DRE 1-binding protein, p37, is YB-1. The human T-cell lymphotropic virus type I (HTLV-I) is associated with a clinically aggressive form of adult T-cell leukemia and the degenerative neuromuscular disease tropical spastic paraparesis/HTLV-I-associated myelopathy. HTLV-I gene expression is regulated at the transcriptional and posttranscriptional levels by viral gene products Tax, (p4Ofax) and Rex, (p27ex) (1, 10, 15, 35). The U3 region of the HTLV-I long terminal repeat (LTR) contains several important elements needed for Tax, transactivation. The 21-bp repeat elements (Tax1-responsive element 1 [TRE-1]) confer Tax,

Background. Somatuline, a somatostatin analogue, as proven to be effective in several animal models of prostate cancer. Preliminary clinical studies also have suggested antitumor activity in patients with prostate cancer. The authors conducted a dose‐escalation trial of 25 patients with metastatic hormone‐refractory prostate cancer. Methods. Dosages of 4, 7, 10, 13, 18, and 24 mg/day were administered by continuous intravenous infusion for at least 28 days. Results. Plasma levels of insulin‐like growth factor‐I (IGF‐I), but not those of IGF‐II, declined modestly during therapy. Toxicities included grade I diarrhea, bloating, infection, nausea, and flatus. The gastrointestinal side effects were typically self‐limiting and occurred during the initial portion of treatment cycles. In addition, three patients experienced grade II catheter‐related infections. No clinical response was noted by either radiographic or tumor marker criteria. The maximally tolerated dose of somatuline was not determined. Conclusion. A continuous intravenous infusion of 24 mg/day of somatuline is well tolerated and could be evaluated in other types of cancer or possibly in less advanced prostate cancer, but no clinical activity was noted at this dose in patients with advanced metastatic hormone‐refractory prostate cancer.

3010 Background: PATHFINDER (NCT04241796) is an interventional, prospective study evaluating implementation of a blood-based multi-cancer early detection (MCED) test that uses targeted methylation-based cfDNA analysis to detect multiple cancer types and simultaneously predict cancer signal origin (CSO). We present a prespecified interim analysis of PATHFINDER evaluating an MCED test in a clinical setting. Methods: Participants (pts; ≥50y) were enrolled into 2 risk cohorts: non-elevated and elevated (smoking history, prior cancer [ > 3y post treatment], or genetic predisposition). MCED test results (cancer signal detected/not detected) were returned to investigators; pts with a signal detected also received a CSO prediction and underwent further diagnostic testing by their medical team. The primary objective was to assess the extent of diagnostic testing needed to achieve diagnostic resolution (eg, time to resolution, number/type of tests). Secondary endpoints included positive predictive value (PPV) and a measure of test satisfaction (following diagnostic resolution [signal detected] and post test [signal not detected]). Results: PATHFINDER consented 6796 pts before closing accrual on 12/4/20; as of October 6, 2020, 4086 consented, 4047 enrolled, and 4033 analyzable pts were included in the interim analysis (62.4% female, 92.1% white). Two study-related adverse events (anxiety of mild severity) were reported. Cancer signal was detected in 1.5% (62/4033) of pts; 40/62 reached diagnostic resolution to date. Kaplan-Meier estimate of median time to resolution was 78 (95% CI, 54-151) days. Among 40 pts that reached diagnostic resolution, ≥1 imaging test was performed in 93% (37/40); ≥1 invasive procedure was performed in 72% (13/18) versus 18% (4/22) of pts with diagnostic resolution of cancer versus no cancer, respectively. Based on results to date, PPV was 45% (95% CI, 30.7-60.2%; 18/40). Of 18 cancer diagnoses, 11 were solid tumors (3 stage IV, 6 stages I-III, 1 metastatic recurrence, 1 missing stage), and 7 were hematologic malignancies (1 stage IV, 4 stages I-III, 2 without AJCC stage). Accuracy of the top CSO prediction in true positives was 82.4% (95% CI, 59.0-93.8%; 14/17). Most pts were satisfied with the test (43.7% extremely satisfied, 30.7% very satisfied, 14.6% satisfied). Signal detection rate and test satisfaction were similar in the 2 risk cohorts; PPV tended to be higher in the elevated risk cohort, as expected. Conclusions: An interim analysis of this return of results study demonstrated promising MCED test results. Of 40 pts achieving diagnostic resolution, nearly half had a diagnostic workup confirming cancer; CSO was predicted with high accuracy for detected cancers. Taken together with the rarity of adverse events and high test satisfaction, these results support the feasibility of clinical implementation. Full enrollment cohort data will be available at the meeting. Clinical trial information: NCT04241796.