ThyroSeq v2 Testing: Impact on Cytologic Diagnosis, Management, and Cost of Care in Patients with Thyroid Nodule

Background: Novel molecular tests (MTs), such as ThyroSeq, may improve the management of thyroid nodules with indeterminate cytologic diagnoses; however, the impact of these tests on cost and outcome of management is unknown. Here, we evaluated the impact of ThyroSeq testing on the cytopathologic diagnosis, management, and cost of care in patients with thyroid nodules. Methods: In a retrospective study, using actual patient cohorts, the outcome and cost of management of patients with thyroid nodules seen before the introduction of ThyroSeq v2 at our institution (standard of care [StC] cohort) were compared with those seen after the introduction of this test (MT cohort). Results: A total of 773 consecutive patients entered the study (393 StC, 380 MT). The incidence of cytologically benign nodules decreased from 71.0% (StC) to 53.2% (MT) and those of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) and follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) increased from 8.9% (StC) to 21.3% (MT) and from 3.1% (StC) to 6.3% (MT), respectively. The overall rate of surgery did not change significantly (23.4% in StC vs. 23.2% in MT). Among patients who underwent surgery, the rate of overtreatment (surgeries performed on histologic benign nodules without clinical indication: compressive symptoms, hyperthyroidism resistant to medication, and nodule size >4 cm) slightly decreased from 18.8% (StC) to 16.7% (MT). The rate of malignancy decreased from 45.5% (StC) to 37.9% (MT) in AUS/FLUS and increased from 40.0% to 53.8% in FN/SFN. However, the overall rate of malignancy remained equal (47.8% in StC vs. 47.7% in MT). The average cost of care per patient in the AUS/FLUS and FN/SFN categories increased from $6,566 (StC) to $8,444 (MT) and from $9,313 (StC) to $10,253 (MT), respectively. Similarly, the overall average cost of care of a patient who underwent thyroid fine-needle aspiration increased from $3,088 (StC) to $4,282 (MT). Finally, the average cost per thyroid cancer detected increased from $26,312 (StC) to $38,746 (MT). Conclusions: Introduction of ThyroSeq v2 resulted in a shift toward indeterminate cytology results. The institutional rate of surgery, overtreatment, and malignancy did not change significantly. Lack of decrease in the rate of surgery along with the additional cost of ThyroSeq v2 increased the overall cost of care of patients including those with indeterminate cytology results.

Differences in Female and Male-to-Female Transgender Facial Skin Micro-Vessel Density

Importance: The risk of hematoma formation after rhytidectomy is gender associated and can lead to postoperative complications. The literature to help explain and elucidate the mechanism behind this gender-associated risk is poorly developed and requires further investigation. Objective: The objective of this study was to compare facial skin micro-vessel density of female and male-to-female (MTF) transgender patients undergoing rhytidectomy to better understand the mechanism of gender-correlated hematoma risk factors. The authors hypothesized that transgender patients would have higher micro-vessel density compared with female patients. Design, Setting, and Participants: This was a prospective histopathological analysis of pre- and post-auricular facial skin samples from patients undergoing primary rhytidectomy. Patient clinical data and skin samples were collected. Histopathological slides were prepared and stained with CD-31, a marker of vessel endothelium, followed by image analysis allowing for micro-vessel stained pixel counts and calculated pixel density comparisons at a single academic hospital. Female, MTF transgender, and male patients >18 years of age were studied. Exposure: Patients undergoing primary rhytidectomy between 2015 and 2018. Main Outcomes: Gender-associated pre- and post-auricular micro-vessel pixel density. Results: Forty-one patients contributed skin samples for analysis. Post-auricular micro-vessel pixel density was greater than pre-auricular density (mean difference post-pre 0.359 percentage points [p.p.], standard error [SE] = 0.135, p = 0.009). The mean post-auricular micro-vessel pixel density was 1.60% (SE = 0.13 p.p.), 2.16% (SE = 0.19 p.p.), and 2.77% (SE = 0.34 p.p.) for female, transgender, and male patients, respectively (p = 0.016). Pre-auricular micro-vessel pixel density showed no difference among females, males, and transgender patients (p = 0.30). Gender was a strong predictor of increased post-auricular micro-vessel pixel density on stepwise linear regression, but it did not predict pre-auricular micro-vessel density. Both preoperative hair removal and a history of hypertension were associated with increased pre-auricular micro-vessel density. Conclusions and Relevance: Facial skin micro-vessel density differs by gender, in addition to pre- and post-auricular locations in patients undergoing rhytidectomy.

Taxonomy of breast cancer based on normal cell phenotype predicts outcome

Accurate classification is essential for understanding the pathophysiology of a disease and can inform therapeutic choices. For hematopoietic malignancies, a classification scheme based on the phenotypic similarity between tumor cells and normal cells has been successfully used to define tumor subtypes; however, use of normal cell types as a reference by which to classify solid tumors has not been widely emulated, in part due to more limited understanding of epithelial cell differentiation compared with hematopoiesis. To provide a better definition of the subtypes of epithelial cells comprising the breast epithelium, we performed a systematic analysis of a large set of breast epithelial markers in more than 15,000 normal breast cells, which identified 11 differentiation states for normal luminal cells. We then applied information from this analysis to classify human breast tumors based on normal cell types into 4 major subtypes, HR0-HR3, which were differentiated by vitamin D, androgen, and estrogen hormone receptor (HR) expression. Examination of 3,157 human breast tumors revealed that these HR subtypes were distinct from the current classification scheme, which is based on estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Patient outcomes were best when tumors expressed all 3 hormone receptors (subtype HR3) and worst when they expressed none of the receptors (subtype HR0). Together, these data provide an ontological classification scheme associated with patient survival differences and provides actionable insights for treating breast tumors.

Abstract B067: Taxonomy of breast cancer based on normal cell phenotype and ontology

The classification of lymphoma and leukemia is successfully done by using normal cell types as a reference point which is one of the many reasons that better therapies are available for their treatment. In case of breast cancer, clinically it is classified as Estrogen Receptor positive, Human Epidermal Growth Factor Receptor 2 (Her2) positive and triple negative breast cancer while in the research settings, it has been classified by mRNA expression profiling but these classification systems are still evolving. Our laboratory attempted to classify breast cancer by examining the expression of different keratin isoforms and Hormone Receptors (HR) studied through immunostaining in 36 normal breast samples and later in 1731 breast tumors from the Nurses' Health Study (NHS) cohort with a patient follow up extending beyond 25 years. Among the various receptors tested, three of these receptors: Androgen Receptor, Estrogen Receptor and Vitamin D Receptor were capable of identifying four major subgroups being designated as HR0-3, depending on the number of hormone receptors present. More importantly, radically different survival outcomes were observed between these HR sub-groups through Kaplan Meier curve analysis; which highlights their usefulness as vital biological markers as wells as targets for breast cancer treatment. Furthermore, the characterization of these HR was carried out in 20 different breast cancer cell lines and the combination of different receptor modulators alone or in combination was attempted with better anti-proliferative effects being observed in the combinatorial group than either treatment alone. Thus, our new classification not only re-classifies breast cancer but also gives insight on how patients could be treated through targeting hormone receptors.

Citation Format: Ankita Thakkar, Sandro Santagata, Ayse Ergonul, Bin Wang, Terri Woo, Rong Hu, J. Chuck Harrell, George McNamara, Matthew Schwede, Aedin C. Culhane, David Kindelberger, Scott Rodig, Andrea Richardson, Stuart J. Schnitt, Rulla M. Tamimi, Tan A. Ince. Taxonomy of breast cancer based on normal cell phenotype and ontology. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr B067.

Predictive value of circulating tumor cells (CTCs) in newly-diagnosed and recurrent ovarian cancer patients

OBJECTIVE

To determine whether circulating tumor cells (CTCs), as detected and enumerated by the Veridex CellSearch system, could predict for clinical outcomes in women with newly diagnosed or recurrent epithelial ovarian cancer.

METHODS

Serial measurements of CTC s and paired serum CA125 were collected in a series of 78 women with newly diagnosed or recurrent ovarian cancer seen at our institution over a period of 15 months. Clinical data were abstracted from patient medical records. CTCs were detected and enumerated by the CellSearch protocol, and patients were divided into CTC negative (<2 CTCs) or positive (≥2 CTCs) groups. CTC groups were correlated with clinical characteristics and outcomes. A longitudinal analysis of CTC change and CA125 trends was also performed.

RESULTS

At least one CTC was isolated from the peripheral blood of over 80% of the women participating in this study, with a range from 0 to 8. No correlations were observed between CTC numbers and clinical characteristics or outcomes. Although both serum CA125 and CTC number exhibited an overall significant decreasing trend over time, there was no correlation observed between change in CTCs and CA125.

CONCLUSION

Using the FDA-approved CellSearch system, CTCs can be isolated from women with newly diagnosed or recurrent ovarian cancer. However, CTC numbers do not significantly correlate with clinical characteristics or patient outcomes. Future studies should focus on phenotypic characterization of CTCs and whether different isolation protocols yield a higher number of CTCs or add prognostic value.

Vascular endothelial growth factors and their receptors and regulators in gestational trophoblastic diseases and normal placenta

OBJECTIVE

To study the expression of vascular endothelial growth factors (VEGFs), placental growth factor (PLGF) and their receptors (VEGFR-1, -2, -3) and their regulators (IL-6, CD147) in normal placenta and gestational trophoblastic disease (GTD) in order to evaluate their potential role in the biology of GTD.

STUDY DESIGN

Paraffin sections of 10 normal, first-trimester placentas, 10 partial moles, 10 complete moles, 5 choriocarcinomas and 5 placental site trophoblastic tumors (PSTTs) were studied immunohistochemically for expression of VEGFR-1, VEGFR-2, VEGFR-3, IL-6, PLGF and CD147. Immunolocalization of VEGF, Angiopoietin-1 and Angiopoietin-2 was performed on 5 choriocarcinomas and 5 PSTTs. The levels of VEGF and VEGFR-2 were determined in supernatants and lysates of normal trophoblast, JEG-3 and JAR choriocarcinoma cells with electrochemiluminescence assays.

RESULTS

The normal placenta had significantly stronger expression of VEGFR-2 than did those of partial and complete mole (p = 0.001, p = 0.003). VEGF, Angiopoietin-1 and Angiopoietin-2 expression in PSTT were significantly higher than those in choriocarcinoma (p = 0.002, p= 0.01, p = 0.038). Choriocarcinoma showed stronger intensity of staining for VEGFR-3 than did normal placenta, partial and complete mole (p = 0.036, p = 0.038, p = 0.05). Choriocarcinoma had significantly stronger staining of CD147 than did partial and complete mole (p<0.01, p<0.01). PSTT exhibited significantly stronger staining for IL-6 than did choriocarcinoma (p = 0.03).

CONCLUSION

PSTTs exhibited strong staining for VEGF, and choriocarcinoma showed strong staining for VEGFR-3. Agents that inhibit the activity of VEGF and VEGF receptors may prove to be useful in the therapy of gestational trophoblastic neoplasia.

Serous tubal intraepithelial carcinoma: diagnostic reproducibility and its implications

Serous tubal intraepithelial carcinoma (STIC) is detected in between 5% and 7% of women undergoing risk-reduction salpingooophorectomy for mutations in the BRCA1 or 2 genes (BRCA+), and seems to play a role in the pathogenesis of many ovarian and "primary peritoneal" serous carcinomas. The recognition of STIC is germane to the management of BRCA+ women; however, the diagnostic reproducibility of STIC is unknown. Twenty-one cases were selected and classified as STIC or benign, using both hematoxylin and eosin and immunohistochemical stains for p53 and MIB-1. Digital images of 30 hematoxylin and eosin-stained STICs (n=14) or benign tubal epithelium (n=16) were photographed and randomized for blind digital review in a Powerpoint format by 6 experienced gynecologic pathologists and 6 pathology trainees. A generalized kappa statistic for multiple raters was calculated for all groups. For all reviewers, the kappa was 0.333, indicating poor reproducibility; kappa was 0.453 for the experienced gynecologic pathologists (fair-to-good reproducibility), and kappa=0.253 for the pathology residents (poor reproducibility). In the experienced group, 3 of 14 STICs were diagnosed by all 6 reviewers, and 9 of 14 by a majority of the reviewers. These results show that interobserver concordance in the recognition of STIC in high-quality digital images is at best fair-to-good for even experienced gynecologic pathologists, and a proportion cannot be consistently identified even among experienced observers. In view of these findings, a diagnosis of STIC should be corroborated by a second pathologist, if feasible.

Utility of chromosomal chromogenic in situ hybridization as an alternative to flow cytometry and cytogenetics in the diagnosis of early partial hydatidiform moles: a validation study

OBJECTIVE

The introduction of p57 immunohistochemistry has aided the distinction between early complete moles (CMs) and hydropic abortus (HA), but no single technique has emerged for the distinction between early partial moles (PMs) and HA. Flow cytometry and cytogenetics have been used, but these require specialized equipment/expertise. The goal of this study is validation of chromosome in situ hybridization (CrISH), focusing on comparing the results to those obtained by cytogenetic methods.

STUDY DESIGN

Archival paraffin blocks from molar and nonmolar gestations were retrieved. Sections were labeled with a chromosome 10 probe. Hybridization and visualization were performed using standard protocols. One hundred nuclei per sample were scored for the number ofsignals.

RESULTS

Of 50 hydatidiform moles, 22 were PMs and 28 were CMs. The CMs showed 2 signals in 25 cases and 4 signals in 3 cases. The PMs showed 3 signals in 21 cases and 2 signals in 1 case. For the HAs there were 2 signals in 24 cases, and 1 case had 3 signals. Concordance between CrISH and flow cytometry studies for molar gestations was 95%.

CONCLUSION

CrlSH is a highly effective adjunct in differentiating between PM and CM and between PM and HA. CrlSH is a simple, cost effective adjunct in evaluating molar gestations.

Polymerase chain reaction detection of HPV in squamous carcinoma of the oropharynx

Human papillomavirus (HPV) testing is routinely performed on oropharyngeal carcinomas. We compared the Access Genetics (Minneapolis, MN) polymerase chain reaction (PCR) assay (AGPCR), DNA-DNA in situ hybridization (ISH; Ventana, Tucson, AZ), and HPV-16 E7 PCR amplification in consecutively accessioned oropharyngeal cancers. We tested 126 cases by both PCR methods; 102 were positive by either for a maximum positive rate (MPR) of 81.0%. Relative to the MPR, the sensitivities of AGPCR and E7 PCR were 90.2% and 72.5%, respectively. Of 17 AGPCR+ cases tested by ISH, 14/14 unequivocally positive/negative were concordant. All cases (97/97) positive by either PCR assay were positive for p16. There was no relationship between level of histologic differentiation and HPV status. ISH and AGPCR have comparable performance for the detection of HPV in oropharyngeal carcinomas. PCR is a suitable and economical assay that is comparable to ISH in sensitivity and may provide logistical advantages relative to ISH for assessing HPV status in oropharyngeal malignancies. However, it is imperative that appropriate sensitivity controls be in place for such assays.

Age related cellular immune response against complete molar pregnancy

OBJECTIVE

Advanced maternal age may result in a weaker immune response against complete molar pregnancy, therefore increasing the risk of gestational trophoblastic neoplasia due to ineffective elimination of the trophoblastic cells after evacuation. The present study was undertaken to investigate the cellular immune response against complete molar pregnancy at the implantation site in younger and older patients.

STUDY DESIGN

Immunolocalization of CD8, granzyme B (GrB), FoxP3 and CD56 was performed on histologic tissue sections prepared from 18 patients aged < or = 40 years and 10 patients aged > 40 years to characterize effector (GrB+CD8+) cytotoxic T cells, GrB positive and negative natural killer cells (CD56) and regulatory T cells (FoxP3+) at the implantation site in complete molar pregnancies.

RESULTS

The number of the different immune cell types did not show significant differences in the implantation sites of complete molar pregnancies between the 2 age groups or between persistent and nonpersistent cases.

CONCLUSION

Immunosenescence of the natural killer and T cells most likely does not play a role in the increased incidence of gestational trophoblastic neoplasia in older patients with complete moles.

Comparison of the Cellsearch Profile Kit (CPK) with the Standard Cellsearch Epithelial Kit (CEK) Demonstrates the CPK Produces Higher Circulating Tumor Cell (CTC) Yields and Is Better Suited for Use in Obtaining CTC's for Molecular Characterization

Background: CTC offer a potential non-invasive approach to obtain and characterize metastatic tumor cells from solid cancers. However, conventional methods for isolating CTC, which use Epcam specific immunomagnetic beads, have been limited by low CTC yields and contaminating leukocytes. We sought to optimize and characterize CTC isolation using the CPK(Veridex LLC) and compare it to conventional methods using the CEK and automated CellTracks counting system, the FDA approved standard. We hypothesized that the CPK, which avoids the potential CTC loss and destruction associated with the multiple washes and labeling steps included in the CEK, would offer improved cell recovery.Methods: We collected two peripheral blood samples from patients (Pts) with metastatic breast cancer (n = 75) and processed them in parallel. Following automated enumeration of the samples with the CEK method, the cells were washed, fixed, and processed as cytospin slides followed by H&E and FISH. Uncounted samples processed with the CPK method were similarly washed, fixed, and processed as cytospin slides, followed by either H&E, IHC (AE1/AE3), IF (HER2, pHER2, EGFR, pEGFR) or FISH using probes against CEP7, EGFR, HER2, and MET.Results: The median cell count from pts with breast cancer using the CPK method was 120 per 7.5 mL of blood (range 4-4967) compared to 4 (range 0-57) using the CEK method (p &lt; 0.0001; t-test). The purity of these cells was high: 59.7 % of cells isolated by CPK (range: 20.9-95.0) were identified as tumor cells by cytokeratin staining while 6.4% (range: 0-21.8) were identified as WBCs by CD45 staining. The remaining 32.3% (range: 4.8-68.0) of cells stained with DAPI only and could not be classified as either tumor cells or lymphocytes, and appeared to have lost their membrane during the isolation. We confirmed the purity of the CTC by HER2 FISH. Among pts whose primary cancer was HER2+ (n=70), 72.4% (range: 44-100%) of CTC had an HER2 gene copy number &gt; 4. From samples isolated from healthy controls (n = 40) and processed using the CPK method the mean total number of cells was 5 per 7.5 mL of blood (range 0-20). These cells were positive for CD45 with only 2 copies of HER2 by FISH. The CPK had low intrapatient variability (CV 9.6%) and samples were stable for at least 72hr. Recovered CTC were well suited for evaluation by IF for phospho antibodies (e.g. pHER2, pAkt), TUNEL (apoptosis), and Ki67 (proliferation). Studies using BC cell lines demonstrated that viable cells could be recovered and propagated with an input as few as 50 cells consistently yielding viable cultures.Conclusion: The CPK technique's relatively high yield, purity, and sample stability make it well suited for use in obtaining CTC's for molecular characterization, including FISH and IF. Assays for mutation detection are currently being evaluated. This technology potentially has a large number of applications in investigating the biology of metastatic cancer as well as in drug development where it can be used to identify predictive biomarkers, mechanisms of resistance, and facilitate pharmacodynamic studies.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3003.

Serous tubal intraepithelial carcinoma: its potential role in primary peritoneal serous carcinoma and serous cancer prevention

PURPOSE

A diagnosis of primary peritoneal serous carcinoma (PPSC) requires exclusion of a source in other reproductive organs. Serous tubal intraepithelial carcinoma (STIC; stage 0) has been described in asymptomatic women with BRCA mutations and linked to a serous cancer precursor in the fimbria. This study examined the frequency of STIC in PPSC and its clinical outcome in BRCA-positive women.

PATIENTS AND METHODS

Presence or absence of STIC was recorded in consecutive cases meeting the 2001 WHO criteria for PPSC, including 26 patients with nonuniform sampling of the fallopian tubes (group 1) and 19 patients with complete tubal examination (group 2; sectioning and extensively examining the fimbriated end, or SEE-FIM protocol). In selected cases, STIC or its putative precursor and the peritoneal tumor were analyzed for p53 mutations (exons 1 to 11). Outcome of STIC was ascertained by literature review.

RESULT

Thirteen (50%) of 26 PPSCs in group 1 involved the endosalpinx, with nine STICs (35%). Fifteen (79%) of 19 cases in group 2 contained endosalpingeal involvement, with nine STICs (47%). STIC was typically fimbrial and unifocal, with variable invasion of the tubal wall. In five of five cases, the peritoneal and tubal lesion shared an identical p53 mutation. Of 10 reported STICs in BRCA-positive women, all patients were without disease on follow-up.

CONCLUSION

The fimbria is the source of nearly one half of PPSCs, suggesting serous malignancy originates in the tubal mucosa but grows preferentially at a remote peritoneal site. The generally low risk of recurrence in stage 0 (STIC) disease further underscores STIC as a possible target for early serous cancer detection and prevention.

Lessons from BRCA: the tubal fimbria emerges as an origin for pelvic serous cancer

Ovarian epithelial cancer is diagnosed in approximately 25,000 women yearly in the United States, accounting for approximately 12,500 deaths. Of these tumors, serous cancer is the most lethal, due to its capacity to spread beyond the reproductive tract and involve the peritoneal surfaces or distant organs. Conventional classification systems designate tumor origins principally on the location of the largest tumor. However, despite the fact that the largest tumors typically involve the ovaries, demonstrations of a precise starting point for these tumors, including precursor lesions, have been inconsistent. In recent years, a major effort to prevent serous cancer in genetically susceptible women with mutations in BRCA1 or BRCA2 has spawned the practice of prophylactic salpingo-oophorectomy. This practice has surprisingly revealed that many early cancers in these women arise in the fallopian tube, and further studies have pinpointed the distal (fimbrial) portion as the most common site of origin. Emerging studies that carefully examine the fallopian tubes suggest a high frequency of early cancer in the fimbria in unselected women with ovarian and peritoneal serous carcinoma, raising the distinct possibility that a significant proportion of these tumors have a fimbrial origin. The evidence for these discoveries and their relevance to serous cancer classification, early detection and prevention are addressed in this review. A model for pelvic serous cancer is proposed that takes into account five distinct variables which ultimately impact on origin and tumor distribution: (1) location of target epithelium, (2) genotoxic stress, (3) type of epithelium, (4) mitigating genetic factors, and (5) tumor spread pattern. Ultimately, this model illustrates the importance of identifying cancer precursors, inasmuch as these entities are useful as both surrogate endpoints for their respective malignancies in epidemiologic studies and natural targets for cancer prevention.

Advances in the recognition of tubal intraepithelial carcinoma: applications to cancer screening and the pathogenesis of ovarian cancer

Prophylactic salpingo-oophorectomies from women with BRCA mutations (BRCA+) have identified the tube as a frequent site of early pelvic serous carcinoma (tubal intraepithelial carcinoma [TIC]). These observations have implications for both the early recognition of pelvic serous carcinoma in susceptible women and determining the ultimate site of origin for pelvic serous carcinomas. Moreover, the unique pathology of TIC has shifted attention from the more exuberant proliferations mentioned in prior studies to a spectrum of neoplastic atypias that can be morphologically subtle. This review addresses a multitude of epithelial changes; benign, malignant, and an intriguing third group, which we term "p53 signatures," is found in benign, nonciliated epithelium and stain intensely positive for p53. Understanding all 3 is important for the proper management of women undergoing prophylactic salpingo-oophorectomy and possibly formulating an integrated model for the pathogenesis of serous carcinoma in the reproductive tract. A protocol for sectioning and extensively examining the fimbriated end (SEE-FIM), and its rationale, is described.

Hyperextension and rotation of head causing internal carotid artery laceration with basilar subarachnoid hematoma

Hyperextension of the head can cause injury to the vessels at the base of the brain. These lacerations are believed to be caused by stretching of the vessels due to the abrupt movement of the head and rotational acceleration of the brain within the cranium, and they usually occur in the intracranial portions of the vessels, producing a subarachnoid hemorrhage. This is the case of a 35-year-old man who received a blow to the face that forcefully hyperextended and rotated his head to the left. Autopsy revealed an intracranial right internal carotid laceration extending from a calcified atherosclerotic plaque. This unusual injury may be due to a combination of blunt force applied to the head and the alteration of the vessel's structural and functional capacities secondary to atherosclerosis.

Cell cycle-regulated transcription of the CLB2 gene is dependent on Mcm1 and a ternary complex factor

Clb2 is the major B-type mitotic cyclin required for entry into mitosis in the budding yeast Saccharomyces cerevisiae. We showed that accumulation of CLB2 transcripts in G2 cells is controlled at the transcriptional level and identified a 55-bp upstream activating sequence (UAS) containing an Mcm1 binding site as being necessary and sufficient for cell cycle regulation. Sequences within the cell cycle-regulated UAS were shown to bind Mcm1 in vitro, and mutation which abolished Mcm1-dependent DNA binding activity eliminated cell cycle-regulated transcription in vivo. A second protein with no autonomous DNA binding activity was also recruited into Mcm1-UAS complexes, generating a ternary complex. A point mutation in the CLB2 UAS which blocked ternary complex formation, but still allowed Mcm1 to bind, resulted in loss of cell cycle regulation in vivo, suggesting that the ternary complex factor is also important in control of CLB2 transcription. We discuss the possibility that the CLB2 gene is coregulated with other genes known to be regulated with the same periodicity and suggest that Mcm1 and the ternary complex factor may coordinately regulate several other G2-regulated transcripts.