Paxillin knockout in mouse granulosa cells increases fecundity†

Paxillin is an intracellular adaptor protein involved in focal adhesions, cell response to stress, steroid signaling, and apoptosis in reproductive tissues. To investigate the role of paxillin in granulosa cells, we created a granulosa-specific paxillin knockout mouse model using Cre recombinase driven by the Anti-Müllerian hormone receptor 2 gene promoter. Female granulosa-specific paxillin knockout mice demonstrated increased fertility in later reproductive age, resulting in higher number of offspring when bred continuously up to 26 weeks of age. This was not due to increased numbers of estrous cycles, ovulated oocytes per cycle, or pups per litter, but this was due to shorter time to pregnancy and increased number of litters in the granulosa-specific paxillin knockout mice. The number of ovarian follicles was not significantly affected by the knockout at 30 weeks of age. Granulosa-specific paxillin knockout mice had slightly altered estrous cycles but no difference in circulating reproductive hormone levels. Knockout of paxillin using clustered regularly interspaced short palindromic repeat-associated protein 9 (CRISPR-Cas9) in human granulosa-derived immortalized KGN cells did not affect cell proliferation or migration. However, in cultured primary mouse granulosa cells, paxillin knockout reduced cell death under basal culture conditions. We conclude that paxillin knockout in granulosa cells increases female fecundity in older reproductive age mice, possibly by reducing granulosa cell death. This study implicates paxillin and its signaling network as potential granulosa cell targets in the management of age-related subfertility.

OR06-2 Paxillin and Androgen Receptor Interact to Modulate Female Fertility

While androgens are traditionally associated with male physiology, recently it has become more apparent that balanced levels of androgens are crucial to maintaining female health and fertility as well. Specifically, androgens are necessary for granulosa cell proliferation and follicle survival and growth. Excess androgen levels in females are a hallmark in polycystic ovary syndrome (PCOS), whereas insufficient androgen signaling due to androgen receptor (AR) knockout leads to diminished ovarian reserve (DOR) – with both extremes resulting in anovulatory infertility. However, little is known about the factors regulating AR in granulosa cells. Our previous findings demonstrate that paxillin, a cytoplasmic adaptor protein, mediates AR signaling in prostate cancer cells. However, our current interest is whether this interaction is also found in granulosa cells. As such, our results show that paxillin indeed enhances AR protein expression in granulosa cells. We have also demonstrated through immunofluorescence and proximity ligation assays that paxillin colocalizes with AR, notably in membrane-bound complexes. Moreover, paxillin-null KGN and mouse granulosa cells express lower levels of AR, as demonstrated through Western blotting and immunofluorescence imaging. We then conducted mRNA and protein degradation experiments in paxillin-null KGN cells in order to determine the mechanism by which paxillin increases AR expression. These results suggest that paxillin acts by preventing AR mRNA and protein degradation, possibly by trafficking AR to focal adhesions, where it may be sequestered from degradation. Finally, to investigate the role of paxillin in female fertility, we developed a novel granulosa cell-specific paxillin knockout mouse model using an Amhr2-driven Cre/lox system. These knockout mice experience altered estrous cycles compared to controls, spending fewer days in estrus and more days in metestrus/diestrus. When bred continuously through 6 months of age, the paxillin KO mice produced significantly more litters compared to their littermate controls. Taken together, these results suggest that paxillin acts as a regulator of androgen-mediated female fertility in granulosa cells, and may serve as a potential target for therapeutics in fertility-related diseases such as PCOS and DOR.

Presentation: Saturday, June 11, 2022 11:45 a.m. - 12:00 p.m.

The role of three dimensional functional lung imaging in radiation treatment planning: the functional dose-volume histogram

PURPOSE

During thoracic irradiation (XRT), treatment fields are usually designed to minimize the volume of nontumor-containing lung included. Generally, functional heterogeneities within the lung are not considered. The three dimensional (3D) functional information provided by single photon emission computed tomography (SPECT) lung perfusion scans might be useful in designing beams that minimize incidental irradiation of functioning lung tissue. We herein review the pretreatment SPECT scans in 86 patients (56 with lung cancer) to determine which are likely to benefit from this technology.

METHODS AND MATERIALS

Prior to thoracic XRT, SPECT lung perfusion scans were obtained following the intravenous injection of approximately 4 mCi of 99mcTc-labeled macro-aggregated albumin. The presence of areas of decreased perfusion, their location relative to the tumor, and the potential clinical usefulness of their recognition, were scored. Patients were grouped and compared (two-tailed chi-square) based on clinical factors. Conventional dose-volume histograms (DVHs) (DVFHs) are calculated based on the dose distribution throughout the computed tomography (CT)-defined lung and SPECT-defined perfused lung, respectively.

RESULTS

Among 56 lung cancer patients, decreases in perfusion were observed at the tumor, adjacent to the tumor, and separate from the tumor in 94%, 74%, and 42% of patients, respectively. Perfusion defects adjacent to the tumor were often large with centrally placed tumors. Hypoperfusion in regions separate from the tumor were statistically most common in patients with relatively poor pulmonary function and chronic obstructive pulmonary disease (COPD). Considering all SPECT defects adjacent to and separate from the tumor, corresponding CT abnormalities were seen in only approximately 50% and 20% of patients, respectively, and were generally not as impressive. Following XRT, hypoperfusion at and separate from the tumor persisted, while defects adjacent to the tumor improved in several patients. In four patients who achieved a complete response scored by CT with chemotherapy prior to XRT, persistent hypoperfusion was present at and adjacent to the tumor site in three. Among 30 patients with cancers not arising in the lung (14 breast, 12 lymphoma, 4 others), perfusion defects were seen in only 4 (2 adjacent and 2 apart). Recognition of decreases in perfusion mainly impacted on treatment planning for a few patients with poor pulmonary function and limited target volumes. DVFHs have been useful in beam selection for patients with marked perfusion heterogeneities.

CONCLUSIONS

Lung perfusion scans provide functional information not provided by CT scans that can be useful in designing radiation treatment beams that minimize incidental irradiation of the function regions of the lung. This approach appears to be most helpful in patients with gross intrathoracic lung cancer, especially those with small targets and relatively poor pulmonary function. One limitation of this approach is that some of the defects adjacent to the tumor site reperfuse following treatment, indicating that these scans identify perfusion rather than potential perfusion. Three dimensional functional data can be used to generate DVFHs that may be more predictive of the physiological consequences of the radiation than conventional DVHs. Additional work is currently underway to test this hypothesis.

A phorbol ester tolerant (PET) variant of HL-60 promyelocytes

The promyelocytic leukaemia cell line HL-60 differentiates to a macrophage-like cell when exposed to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) and other agents which activate protein kinase C. To investigate this phenomenon we developed an HL-60 variant which does not differentiate when exposed to TPA. HL-60 cells were exposed to the mutagen ethyl methanesulphonate and were cloned in soft agar in the presence of a normally lethal concentration of TPA. One colony of cells that proliferated in TPA was obtained. The cells of this phorbol ester tolerant (PET) line have retained their resistance to TPA for several years without selective pressure. They are somewhat larger than their phorbol ester sensitive (S) parent, but they are otherwise morphologically similar. When PET-cells are exposed to TPA their growth is arrested for approximately 48 h. Thereafter, they resume their original rate of replication at all concentrations of TPA tested. S-cells undergo changes typical of HL-60 when exposed to TPA; they aggregate, stop growing, adhere to the flask and die. The PET-cells appeared to be as sensitive as S-cells to other agents which differentiate HL-60 such as retinoic acid, dimethysulphoxide, and 1,25-dihydroxyvitamin D3, as determined by rate of proliferation in culture, Wright's stain, nitroblue tetrazolium reduction, and induction of the ectoenzyme NAD-glycohydrolase. TPA-induced protein phosphorylation was studied using one- and two-dimensional polyacrylamide gel electrophoresis. Several proteins increased their incorporation of 32P when S- and PET-cells were exposed to TPA, the most prominent of which were the two previously described nuclear matrix proteins of 80 kd and 33 kd. There was no difference in the protein phosphorylation pattern in S- and PET-cells, nor in how this pattern changed on TPA exposure. Fluorescent activated cell sorting and karyotypic analysis revealed PET-cells to be a hypotetraploid variant of S-cells, with approximately 80 chromosomes, including a marker chromosome iso(1p) not found in the S-cells. Identification of the biochemical lesion responsible for this TPA resistance in PET cells will provide clues concerning the mechanism of this important pathway for the induction of cell differentiation.