Safety and efficacy of panitumumab in combination with trifluridine/tipiracil for pre-treated patients with unresectable, metastatic colorectal cancer with wild-type RAS: The phase 1/2 APOLLON study.

BACKGROUND: We aimed to assess the safety and efficacy of combination treatment with panitumumab plus trifluridine/tipiracil (FTD/TPI) in patients with wild-type RAS metastatic colorectal cancer (mCRC) who were refractory/intolerant to standard therapies other than anti-epidermal growth factor receptor therapy. METHODS: APOLLON was an open-label, multicentre, phase 1/2 trial. In the phase 1 part, 3 + 3 de-escalation design was used to investigate the recommended phase 2 dose (RP2D); all patients in the phase 2 part received the RP2D. The primary endpoint was investigator-assessed progression-free survival (PFS) rate at 6 months. Secondary endpoints included PFS, overall survival (OS), overall response rate (ORR), disease control rate (DCR), time to treatment failure (TTF), and safety. RESULTS: Fifty-six patients were enrolled (phase 1, n = 7; phase 2, n = 49) at 25 Japanese centres. No dose-limiting toxicities were observed in patients receiving panitumumab (6 mg/kg every 2 weeks) plus FTD/TPI (35 mg/m2 twice daily; days 1-5 and 8-12 in a 28-day cycle), which became RP2D. PFS rate at 6 months was 33.3% (90% confidence interval [CI] 22.8-45.3). Median PFS, OS, ORR, DCR, and TTF were 5.8 months (95% CI 4.5-6.5), 14.1 months (95% CI 12.2-19.3), 37.0% (95% CI 24.3-51.3), 81.5% (95% CI 68.6-90.8), and 5.8 months (95% CI 4.29-6.21), respectively. Neutrophil count decreased (47.3%) was the most common Grade 3/4 treatment-emergent adverse event. No treatment-related deaths occurred. CONCLUSION: Panitumumab plus FTD/TPI exhibited favourable anti-tumour activity with a manageable safety profile and may be a therapeutic option for pre-treated mCRC patients.

Panitumumab interaction with TAS-102 leads to combinational anticancer effects via blocking of EGFR-mediated tumor response to trifluridine.

Panitumumab is a monoclonal antibody developed against the human epidermal growth factor receptor (EGFR). TAS-102 is a novel chemotherapeutic agent containing trifluridine (FTD) as the active cytotoxic component. Both panitumumab and TAS-102 have been approved for the treatment of metastatic colorectal cancer. In this study, we revealed the mechanism underlying the anticancer effects of panitumumab/TAS-102 combination using preclinical models. Panitumumab/FTD cotreatment showed additive antiproliferative effects in LIM1215 and synergistic antiproliferative effects in SW48 colon cancer cells. Consistent with the in vitro effects, panitumumab/TAS-102 combination caused tumor regression in LIM1215 and COL-01-JCK colon cancer patient-derived xenograft models. In LIM1215 cells, FTD induced extracellular signal-regulated kinase (ERK)/protein kinase B (AKT)/signal transducer and activator of transcription 3 (STAT3) phosphorylation and subsequent serine/threonine phosphorylation of EGFR, while it had no effects on EGFR tyrosine phosphorylation. Panitumumab and the tyrosine kinase inhibitor erlotinib reduced the basal level of EGFR tyrosine phosphorylation and reversed FTD-induced ERK/AKT/STAT3 and EGFR serine/threonine phosphorylation. These results suggested that FTD in combination with the basal activity of EGFR tyrosine kinase induced downstream prosurvival signaling through ERK/AKT/STAT3 phosphorylation. Collectively, we propose that panitumumab interacts with FTD by targeting EGFR-mediated adaptive responses, thereby exerting anticancer effects when used in combination with TAS-102. These preclinical findings provide a compelling rationale for evaluating the combination of anti-EGFR antibodies with TAS-102 against metastatic colorectal cancer.

Pegylated recombinant human megakaryocyte growth and development factor suppresses the development of megakaryoblastic leukemia in mice.

We examined the effects of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) on the development of L-8057, a murine megakaryoblastic leukemia that expresses the thrombopoietin receptor c-Mpl, in mice. PEG-rHuMGDF administration prolonged survival of L-8057 leukemic mice, in which L-8057 cell growth in the spleen was decreased. L-8057 cells harvested from PEG-rHuMGDF-treated leukemic mice had decreased ability to generate leukemic colonies in vitro as well as to induce leukemia in vivo. PEG-rHuMGDF administration also resulted in prolonged survival of mice transplanted with a c-Mpl-expressing erythroleukemia, but had no effect on survival of mice transplanted with a myeloblastic leukemia that does not possess c-Mpl. Thus, PEG-rHuMGDF suppresses the development of c-Mpl-expressing leukemia in vivo in mice.

Identification of two novel clusters of ultrahigh-sulfur keratin-associated protein genes on human chromosome 11.

We analyzed two novel clusters of keratin-associated protein (KAP) genes on human chromosome 11 (11p15.5 and 11q13.5) in which we identified two known human KRTAP5 genes, KerA (=KRN1) and KerB, and nine novel KRTAP5 family genes. RT-PCR analysis of these KAP genes showed preferential expression in human hair root, suggesting these gene products are required for hair formation. Based on the deduced amino acid sequences, all these KAP proteins were classified into an ultrahigh-sulfur (UHS) type KAP with high cysteine content (> 30 mol%). These KAPs also showed high glycine and serine contents (average 24.30 and 21.13 mol%, respectively), distinguishing from other UHS/HS KAP families located on human chromosomes 17 and 21. Dot-matrix analysis revealed a significant similarity between these two KAP gene clusters. We postulated a mechanism by which these two KAP gene clusters are generated via genomic duplication of a primordial gene cluster followed by genetic modification during evolution.

A cluster of 21 keratin-associated protein genes within introns of another gene on human chromosome 21q22.3.

Recently, we identified multiple unique sequences in the 21q22.3 region and predicted them to be a cluster of genes encoding hair-specific keratin-associated proteins (KAPs). Detailed computer-aided analysis of these clustered genes revealed that the cluster spans over 165 kb and consists of 21 KAP-related sequences including 16 putative genes and 5 pseudogenes. These were further divided into two subfamilies, KRTAP12 (KRTAP12.1-12.4 and KRTAP12.5P) and KRTAP18 (KRTAP18.1-18.12 and KRTAP18.13P-18.16P). All 16 putative genes possess several intragenic repeat sequences and apparently belong to the high-sulfur KAP gene family (16-30% cysteine content) known for nonhuman mammalian species. Transcripts were detected by RT-PCR analysis for all 16 putative KAP genes and their expression was restricted to hair root cells (radix pili cells) and not found in 28 other tissues, including skin. All 16 KAP genes produced unspliced transcripts, indicating their nature to be that of active intronless genes. Interestingly, all these KAP-related genes are located within introns of the recently identified gene TSPEAR (approved gene symbol C21orf29), 214 kb in size. Surprisingly, the transcriptional direction of 8 of the 16 active genes is the same as that of C21orf29/TSPEAR. This finding suggests a novel transcription mechanism in which C21orf29/TSPEAR gene transcription passes over the multiple transcriptional termination sites of the KAP genes.

The transmembrane serine protease (TMPRSS3) mutated in deafness DFNB8/10 activates the epithelial sodium channel (ENaC) in vitro.

TMPRSS3 encodes a transmembrane serine protease that contains both LDLRA and SRCR domains and is mutated in non-syndromic autosomal recessive deafness (DFNB8/10). To study its function, we cloned the mouse ortholog which maps to Mmu17, which is structurally similar to the human gene and encodes a polypeptide with 88% identity to the human protein. RT-PCR and RNA in situ hybridization on rat and mouse cochlea revealed that Tmprss3 is expressed in the spiral ganglion, the cells supporting the organ of Corti and the stria vascularis. RT-PCR on mouse tissues showed expression in the thymus, stomach, testis and E19 embryos. Transient expression of wild-type or tagged TMPRSS3 protein showed a primary localization in the endoplasmic reticulum. The epithelial amiloride-sensitive sodium channel (ENaC), which is expressed in many sodium-reabsorbing tissues including the inner ear and is regulated by membrane-bound channel activating serine proteases (CAPs), is a potential substrate of TMPRSS3. In the Xenopus oocyte expression system, proteolytic processing of TMPRSS3 was associated with increased ENaC mediated currents. In contrast, 6 TMPRSS3 mutants (D103G, R109W, C194F, W251C, P404L, C407R) causing deafness and a mutant in the catalytic triad of TMPRSS3 (S401A), failed to undergo proteolytic cleavage and activate ENaC. These data indicate that important signaling pathways in the inner ear are controlled by proteolytic cleavage and suggest: (i) the existence of an auto-catalytic processing by which TMPRSS3 would become active, and (ii) that ENaC could be a substrate of TMPRSS3 in the inner ear.

Marked improvement of thrombocytopenia in a murine model of idiopathic thrombocytopenic purpura by pegylated recombinant human megakaryocyte growth and development factor.

OBJECTIVE: We examined the stimulatory effect of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) on platelet production in male (NZW x BXSB) F(l) (W/B F(1)) mice, a murine model of idiopathic thrombocytopenic purpura. MATERIALS AND METHODS: A cohort of 19- to 25-week-old, severely thrombocytopenic male W/B F(1) mice were given PEG-rHuMGDF at different dosing schedules. Before and at various times after therapy, platelet counts, reticulated platelets, platelet lifespan, and levels of platelet-associated immunoglobulin G were measured. Analysis of megakaryocytic cells was performed. RESULTS: Treatment of male W/B F(1) mice with PEG-rHuMGDF (30 microg/kg/day) three times per week for several weeks resulted in sustained thrombocytosis, accompanied by increased megakaryocytopoiesis in both the bone marrow and spleen. The degree of the platelet response to PEG-rHuMGDF varied between individual mice, likely reflecting the heterogeneity of the disease. Production of new platelets in response to PEG-rHuMGDF was manifested by an increase in reticulated platelets. Levels of platelet-associated immunoglobulin G decreased inversely during periods of thrombocytosis. PEG-rHuMGDF therapy also improved thrombocytopenia in male W/B F(1) mice refractory to splenectomy. Platelet lifespan was not affected by PEG-rHuMGDF. Male W/B F(1) mice treated with pegylated murine MGDF, a homologue of PEG-rHuMGDF, had persistent thrombocytosis for at least 7 months, suggesting that antiplatelet antibody production was not enhanced. CONCLUSIONS: PEG-rHuMGDF therapy potently stimulated platelet production, effectively ameliorating thrombocytopenia in a murine model of idiopathic thrombocytopenic purpura.