Immunohistochemical expression of neural cell adhesion molecule in Wilms tumors, nephrogenic rests, and fetal and postnatal renal cortices

Altered binding affinity of SIX1-Q177R correlates with enhanced WNT5A and WNT pathway effector expression in Wilms tumor

Wilms tumors present as an amalgam of varying proportions of tissues located within the developing kidney, one being the nephrogenic blastema comprising multipotent nephron progenitor cells (NPCs). The recurring missense mutation Q177R in NPC transcription factors SIX1 and SIX2 is most correlated with tumors of blastemal histology and is significantly associated with relapse. Yet, the transcriptional regulatory consequences of SIX1/2-Q177R that might promote tumor progression and recurrence have not been investigated extensively. Utilizing multiple Wilms tumor transcriptomic datasets, we identified upregulation of the gene encoding non-canonical WNT ligand WNT5A in addition to other WNT pathway effectors in SIX1/2-Q177R mutant tumors. SIX1 ChIP-seq datasets from Wilms tumors revealed shared binding sites for SIX1/SIX1-Q177R within a promoter of WNT5A and at putative distal cis-regulatory elements (CREs). We demonstrate colocalization of SIX1 and WNT5A in Wilms tumor tissue and utilize in vitro assays that support SIX1 and SIX1-Q177R activation of expression from the WNT5A CREs, as well as enhanced binding affinity within the WNT5A promoter that may promote the differential expression of WNT5A and other WNT pathway effectors associated with SIX1-Q177R tumors.

ADVL1522: A phase 2 study of lorvotuzumab mertansine (IMGN901) in children with relapsed or refractory wilms tumor, rhabdomyosarcoma, neuroblastoma, pleuropulmonary blastoma, malignant peripheral nerve sheath tumor, or synovial sarcoma-A Children's Oncology Group study

BACKGROUND

Lorvotuzumab mertansine (IMGN901) is an antibody-drug conjugate linking an antimitotic agent (DM1) to an anti-CD56 antibody (lorvotuzumab). Preclinical efficacy has been noted in Wilms tumor, rhabdomyosarcoma, and neuroblastoma. Synovial sarcoma, malignant peripheral nerve sheath tumor (MPNST), and pleuropulmonary blastoma also express CD56. A phase 2 trial of lorvotuzumab mertansine was conducted to assess its efficacy, recommended phase 2 dose, and toxicities.

METHODS

Eligible patients had relapsed after or progressed on standard therapy for their tumor type. Lorvotuzumab mertansine (110 mg/m² per dose) was administered at the adult recommended phase 2 dose intravenously on days 1 and 8 of 21-day cycles. Dexamethasone premedication was used. Pharmacokinetic samples, peripheral blood CD56-positive cell counts, and tumor CD56 expression were assessed.

RESULTS

Sixty-two patients enrolled. The median age was 14.3 years (range, 2.8-29.9 years); 35 were male. Diagnoses included Wilms tumor (n = 17), rhabdomyosarcoma (n = 17), neuroblastoma (n = 12), synovial sarcoma (n = 10), MPNST (n = 5), and pleuropulmonary blastoma (n = 1). Five patients experienced 9 dose-limiting toxicities: hyperglycemia (n = 1), colonic fistula (n = 1) with perforation (n = 1), nausea (n = 1) with vomiting (n = 1), increased alanine aminotransferase in cycle 1 (n = 2), and increased alanine aminotransferase in cycle 2 (n = 1) with increased aspartate aminotransferase (n = 1). Non-dose-limiting toxicities (grade 3 or higher) attributed to lorvotuzumab mertansine were rare. The median values of the maximum concentration, half-life, and area under the curve from zero to infinity for DM1 were 0.87 µg/mL, 35 hours, and 27.9 µg/mL h, respectively. Peripheral blood CD56+ leukocytes decreased by 71.9% on day 8. One patient with rhabdomyosarcoma had a partial response, and 1 patient with synovial sarcoma achieved a delayed complete response.

CONCLUSIONS

Lorvotuzumab mertansine (110 mg/m² ) is tolerated in children at the adult recommended phase 2 dose; clinical activity is limited.

Arterial flow regulator enables transplantation and growth of human fetal kidneys in rats

Here we introduce a novel method of transplanting human fetal kidneys into adult rats. To overcome the technical challenges of fetal-to-adult organ transplantation, we devised an arterial flow regulator (AFR), consisting of a volume adjustable saline-filled cuff, which enables low-pressure human fetal kidneys to be transplanted into high-pressure adult rat hosts. By incrementally withdrawing saline from the AFR over time, blood flow entering the human fetal kidney was gradually increased until full blood flow was restored 30 days after transplantation. Human fetal kidneys were shown to dramatically increase in size and function. Moreover, rats which had all native renal mass removed 30 days after successful transplantation of the human fetal kidney were shown to have a mean survival time of 122 days compared to 3 days for control rats that underwent bilateral nephrectomy without a prior human fetal kidney transplant. These in vivo human fetal kidney models may serve as powerful platforms for drug testing and discovery.

Immunohistochemical expression of GLUT1 and its correlation with unfavorable histology and TP53 codon 72 polymorphism in Wilms tumors

Reprogramming of energy metabolism, such as increased glycolysis, is a hallmark of cancer cells. One mechanism by which cancer cells fuel glycolysis is through increased uptake of glucose across cell membranes via the glucose transporter GLUT1. One of the transcriptional repressors of GLUT1 is wild-type TP53, and cancer-associated loss of function mutations within the DNA-binding domain of TP53 impairs the repressive effect of TP53 on transcriptional activity of the GLUT1 gene promoter. Because TP53 mutations are associated with unfavorable histology (diffuse anaplasia) in Wilms tumors, we hypothesized increased expression of GLUT1 in these tumors. To evaluate this hypothesis, we performed tissue microarray-based immunohistochemistry for GLUT1 in a set of 50 Wilms tumors, including 5 with unfavorable histology. In a subset of 16 favorable histology Wilms tumors, we compared the GLUT1 immunoexpression with TP53 codon 72 polymorphism status. We found consistently stronger immunoexpression of GLUT1 in unfavorable histology Wilms tumors compared to favorable histology Wilms tumors (P  =  0.04). We noted that the favorable histology Wilms tumors with a proline residue at position 72 of TP53 tended to have higher immunoexpression of GLUT1, although this immunoexpression did not reach statistical significance in this small set of cases. In summary, our finding of strong GLUT1 immunoexpression in unfavorable histology Wilms tumors indicates that these tumors are likely to be 2-deoxy-2-((18)F)fluoro-d-glucose avid and that GLUT1 should be evaluated as a therapeutic target for these tumors that otherwise show resistance to conventional therapy.

Activated NOTCH2 is overexpressed in hepatoblastomas: an immunohistochemical study

Hepatoblastoma is a pediatric malignancy characterized by the uncontrolled proliferation of immature hepatocytes (hepatoblasts). This disease is diagnosed primarily in children younger than 5 years and is disproportionately observed in former premature infants. Cytogenetically, hepatoblastoma is characterized by numerical aberrations, as well as unbalanced translocations involving the proximal region of chromosome 1q. The NOTCH2 gene has been mapped to this locus, and it is well established that the NOTCH gene family is an important regulator of several developmental pathways. Specifically, the NOTCH2 protein is known to delay hepatoblast maturation during early hepatic organogenesis, and the reduction of NOTCH2 expression correlates with the differentiation of hepatoblasts into hepatocytes and biliary cells in the developing liver. We hypothesized that NOTCH2 is involved in the pathogenesis of hepatoblastoma by maintaining a population of undifferentiated hepatoblasts. We studied the immunohistochemical expression of NOTCH2 and its isoforms NOTCH1, NOTCH3, and NOTCH4 and the NOTCH2 primary ligand JAGGED1 in hepatoblastomas. Compared with the normal liver, an increased level of NOTCH2 expression was seen in 22 of 24 (92%) hepatoblastomas. There was no significant staining for other NOTCH isoforms and JAGGED1 in hepatoblastomas. Therefore, we suggest that NOTCH2 expression and activation, independent of JAGGED1 expression, may contribute to the pathogenesis of hepatoblastoma. In the hepatoblastoma sinusoidal vasculature, we saw NOTCH3 and NOTCH1 expression. These observations have potential implications with regard to therapeutic targeting of the NOTCH signaling pathway in hepatoblastomas.