Nuclear Transport Factor 2 (NTF2) suppresses WM983B metastatic melanoma by modifying cell migration, metastasis, and gene expression

While changes in nuclear structure and organization are frequently observed in cancer cells, relatively little is known about how nuclear architecture impacts cancer progression and pathology. To begin to address this question, we studied Nuclear Transport Factor 2 (NTF2) because its levels decrease during melanoma progression. We show that increasing NTF2 expression in WM983B metastatic melanoma cells reduces cell proliferation and motility while increasing apoptosis. We also demonstrate that increasing NTF2 expression in these cells significantly inhibits metastasis and prolongs survival of mice. NTF2 levels affect the expression and nuclear positioning of a number of genes associated with cell proliferation and migration, and increasing NTF2 expression leads to changes in nuclear size, nuclear lamin A levels, and chromatin organization. Thus, ectopic expression of NTF2 in WM983B metastatic melanoma abrogates phenotypes associated with advanced stage cancer both in vitro and in vivo, concomitantly altering nuclear and chromatin structure and generating a gene expression profile with characteristics of primary melanoma. We propose that NTF2 is a melanoma tumor suppressor and could be a novel therapeutic target to improve health outcomes of melanoma patients.

The nuclear transport factor CSE1 drives macronuclear volume increase and macronuclear node condensation in Stentor coeruleus

The giant ciliate, Stentor coeruleus, provides a unique opportunity to study nuclear shape because its macronucleus undergoes a rapid, dramatic, and developmentally regulated shape change. During a 2 hour time period within cell division and regeneration, the 400 um long moniliform macronucleus condenses into a single mass, elongates into a vermiform shape, and then renodulates, returning to its original beads-on-a-string morphology (Tartar 1961). Previous work from the 1960s - 1980s demonstrated that the macronuclear shape change is a highly regulated part of cell division and regeneration, but there were no molecular studies into this process (De Terra 1964; De Terra 1983). With the recent availability of a sequenced Stentor genome, a transcriptome during regeneration, and molecular tools like RNAi, it is now possible to investigate the molecular mechanisms that drive macronuclear shape change (Slabodnick et al. 2014; Slabodnick et al. 2017; Sood et al. 2021). We found that the volume of the macronucleus increases during condensation. When the nuclear transport factor, CSE1, is knocked down by RNAi, this volume increase is reduced, and the nodes are unable to fuse. This affects the final morphology of the macronucleus: 24 hours after regeneration the macronucleus is misshapen. We found that CSE1 is mainly cytoplasmic during interphase and in early regeneration, and then becomes mainly macronuclear during condensation. At the end of regeneration CSE1 is degraded while the macronucleus returns to its pre-condensation volume. We propose a model in which nuclear transport via CSE1 increases the volume of the macronucleus, driving the condensation of the many nodes into a single mass.

Nuclear Transport Factor 2 (NTF2) suppresses metastatic melanoma by modifying cell migration, metastasis, and gene expression

SUMMARYWhile changes in nuclear structure and organization are frequently observed in cancer cells, relatively little is known about how nuclear architecture impacts cancer progression and pathology. To begin to address this question, we studied Nuclear Transport Factor 2 (NTF2) because its levels decrease during melanoma progression. We show that increasing NTF2 expression in metastatic melanoma cells reduces cell proliferation and motility while increasing apoptosis. We also demonstrate that increasing NTF2 expression in these cells significantly inhibits metastasis and increases survival of mice. Mechanistically, we show that NTF2 levels affect the expression and nuclear positioning of a number of genes associated with cell proliferation and migration. We propose that by decreasing nuclear size and/or lamin A nuclear localization, ectopic expression of NTF2 in metastatic melanoma alters chromatin organization to generate a gene expression profile with characteristics of primary melanoma, concomitantly abrogating several phenotypes associated with advanced stage cancer both in vitro and in vivo. Thus NTF2 acts as a melanoma tumor suppressor to maintain proper nuclear structure and gene expression and could be a novel therapeutic target to improve health outcomes of melanoma patients.