Protein kinase C-beta activates tyrosinase by phosphorylating serine residues in its cytoplasmic domain

We have previously shown that protein kinase C-beta (PKC-beta) is required for activation of tyrosinase (Park, H. Y., Russakovsky, V., Ohno, S., and Gilchrest, B. A. (1993) J. Biol. Chem. 268, 11742-11749), the rate-limiting enzyme in melanogenesis. We now examine its mechanism of activation in human melanocytes. In vivo phosphorylation experiments revealed that tyrosinase is phosphorylated through the PKC-dependent pathway and that introduction of PKC-beta into nonpigmented human melanoma cells lacking PKC-beta lead to the phosphorylation and activation of tyrosinase. Preincubation of intact melanosomes with purified active PKC-beta in vitro increased tyrosinase activity 3-fold. By immunoelectron microscopy, PKC-beta but not PKC-alpha was closely associated with tyrosinase on the outer surface of melanosomes. Western blot analysis confirmed the association of PKC-beta with melanosomes. Only the cytoplasmic (extra-melanosomal) domain of tyrosinase, which contains two serines but no threonines, was phosphorylated by the serine/threonine kinase PKC-beta. These two serines at positions 505 and 509 both are present in the C-terminal peptide generated by trypsin digestion of tyrosinase. Co-migration experiments comparing synthetic peptide standards of all three possible phosphorylated tryptic peptides, a diphosphopeptide and two monophosphopeptides, to tyrosinase-phosphorylated in intact melanocytes by PKC-beta and then subjected to trypsin digestion revealed that both serine residues are phosphorylated by PKC-beta. We conclude that PKC-beta activates tyrosinase directly by phosphorylating serine residues at positions 505 and 509 in the cytoplasmic domain of this melanosome-associated protein.

Effects and Role of Multikinase Inhibitors in Thyroid Cancer

BACKGROUND

Thyroid cancer is the most common type of endocrine neoplasia. Differentiated thyroid carcinoma (DTC) represents 94% of all thyroid cancer types. Approximately 20% experience local recurrence and 10% distant metastasis. The recurrent DTC often becomes less differentiated, loses the iodine uptake capability and consequently loses the radioactive iodine treatment option. Under these circumstances survivability drops below 10% at 10 years. The treatment options for dedifferentiated thyroid cancers are extremely limited. This category sometimes referred to as poorly differentiated thyroid cancer (PDTC), is characterised by a missing response to radioiodine treatment and a remarkably reduced survivability. Therefore, new drugs have been developed to fill this gap in treatment.

METHODS

The goal of this work is to review the effects and roles of the multikinase inhibitors sorafenib, sunitinb and lenatinib in thyroid cancer.

RESULTS

The new tyrosine kinase inhibitors (TKIs) aimed to inhibit tumour angiogenesis. Current clinical trials with novel drugs have shown promising results. A phase III trial (DECISION) of sorafenib in radioiodine (RAI)-refractory thyroid cancer showed a median progression-free survival (PFS) of 10.8 months in the sorafenib group, compared to 5.8 months in the placebo group. Sunitinib, another TKI, exhibited significant antitumour effects in patients with advanced DTC. Nevertheless, treatment with TKIs can lead to the development of resistance against these anti-angiogenic treatments, partly due to compensatory mechanisms. Lenvatinib, the recently approved drug for RAI-refractory thyroid cancer, blocks a different receptor than the currently available drugs. Lenvatinib inhibits fibroblast growth factor receptor (FGFR), as well as other receptors. FGFR plays a key role in the development of resistance against anti-angiogenic drugs. In a phase III trial (SELECT) on RAI-refractory DTC, the lenvatinib group showed a PFS of 18.3 months, compared to 3.6 months in the placebo group. This led to the approval of lenvatinib, the first drug capable of reversing anti-angiogenic mechanisms.

CONCLUSION

The frequently adverse effects seen in TKI treatment require further investigation. A well-adjusted balance between efficacy and adverse effects is desirable. No effects on overall survival were reported. Therefore, further studies are required.

Can combining vaginal and rectal progesterone achieve the optimum progesterone range required for implantation in the HRT-FET model?

RESEARCH QUESTION

What is the ongoing pregnancy rate (OPR) in frozen embryo transfer (FET) cycles, using combined rectal and vaginal progesterone in hormonal replacement therapy (HRT)?

DESIGN

A prospective cohort study (n = 277) including 239 HRT-FET cycles with serum progesterone measurements studying combined vaginal (90 mg/12 h) and rectal (90 mg/12 h) progesterone administration and single blastocyst transfer on the sixth day of progesterone administration. A total of 134 responses to questionnaires covering convenience and side-effects were collected.

RESULTS

The median serum progesterone level was 45 nmol/l (range 2-150 nmol/l). Overall positive HCG rate, OPR at week 12 and pregnancy loss rates were 62%, 44% and 29%, respectively. A non-linear relationship between serum progesterone levels and OPR was found. Crude odds ratio for OPR in the high progesterone group (>45 nmol/l) was 0.56 (95% CI 0.32 to 0.98; P = 0.04) compared with the intermediate progesterone group (28-45 nmol/l). Discomfort after rectal progesterone administration was reported on the embryo transfer day and on the day of pregnancy scan 5 weeks later by a total of 18% (16/87) and 17% (8/47) of patients, respectively. Discomfort related to vaginal administration increased significantly over time and was reported by 18% (16/87) on the day of embryo transfer compared with 45% (21/47) on the day of pregnancy scan (P < 0.002).

CONCLUSIONS

Combined rectal and vaginal progesterone in HRT-FET cycles resulted in higher median progesterone levels compared with vaginal administration alone. This study suggests that an upper threshold for serum progesterone exists and that above this concentration serum progesterone levels decrease the OPR. Rectally administered progesterone was well tolerated by patients.

In a real-life setting, risk factors, coronary artery calcium score, and coronary stenosis at computed tomography angiography are associated with major adverse cardiovascular events and all-cause mortality among kidney transplant candidates

Kidney failure is associated with an increased risk of cardiovascular disease and death. This single-center, a retrospective study evaluated the association between risk factors, coronary artery calcium score (CACS), coronary computed tomography angiography (CTA), major adverse cardiovascular events (MACEs), and all-cause mortality in kidney transplant candidates. Data on clinical risk factors, MACE, and all-cause mortality were collected from patient records. A total of 529 kidney transplant candidates were included (median follow-up of 4.7 years). CACS was evaluated in 437 patients and CTA in 411. Both the presence of ≥3 risk factors, CACS of ≥400, as well as multiple-vessel stenoses or left main artery disease predicted MACE (hazard ratio, 2.09; [95% confidence interval, 1.35-3.23]; 4.65 [2.20-9.82]; 3.70 [1.81-7.57]; 4.90 [2.40-10.01]) and all-cause mortality (harad ratio, 4.44; [95% confidence interval, 2.54-7.76]; 4.47 [2.22-9.02]; 2.82 [1.34-5.94]; 5.41 [2.81-10.41]) in univariate analyses. Among patients eligible for CACS and CTA (n = 376), only CACS and CTA were associated with both MACE and all-cause mortality. In conclusion, risk factors, CACS, and CTA provide information on the risk of MACE and mortality in kidney transplant candidates. An additional value of CACS and CTA compared with risk factors was observed for the prediction of MACE in a subpopulation undergoing both CACS and CTA.

Extended anticoagulation after venous thromboembolism

INTRODUCTION

Venous thromboembolism (VTE) carries a high risk of recurrence, and this risk is strongly related to the nature of the index event. Thus, extended anticoagulation treatment is recommended for patients with a high recurrence risk and should be considered for patients with an intermediate risk. This study aimed to provide insight into the clinical practice of extended anticoagulation for VTE patients METHODS. This was a retrospective study of VTE patients covering the period from January 2020 through June 2021. We categorised patients by their estimated risk of recurrence as low (less-than 3% per year), intermediate (3-8% per year) or high (> 8% per year). The decision to stop or extend anticoagulation was made in a multidisciplinary VTE clinic.

RESULTS

A total of 343 patients were included; 315 patients were eligible for analysis. The majority of patients (58.7%) had an intermediate recurrence risk. In total 80.3% received extended treatment. The use was highest (97.9%) among patients with a high recurrence risk, whereas 82.7% with an intermediate risk and 15.2% with a low risk received extended therapy. Non-vitamin K antagonist oral anticoagulants were preferred for extended therapy (82.2%), whereas 5.1% received warfarin and 12.6% low molecular weight heparin.

CONCLUSIONS

In this real-world clinic, the majority of VTE patients switched to extended treatment after initial standard anticoagulation. The role of patient and physician preference as determinants driving this decision should be investigated further.

FUNDING

This study received an unrestricted grant from Bayer, which had no involvement in the study design, data collection, analysis, or manuscript preparation.

TRIAL REGISTRATION

Not relevant.

P-298 The live birth rate of the endometriosis patient is significantly increased by high luteal phase serum progesterone in HRT-FET cycles - A cohort study

Study question

What is the optimal serum progesterone (P4) cut-off level for endometriosis patients undergoing hormone replacement therapy frozen embryo transfer (HRT-FET) with intensive exogenous progesterone luteal phase support?

Summary answer

Endometriosis patients with luteal serum P4 levels≥118nmol/l had significantly higher live birth rates (LBR) compared to patients with lower P4 levels.

What is known already

A low luteal serum P4 level decreases the reproductive outcome of HRT-FET cycles in the “standard” patient, and an optimal cut-off level of 10ng/ml has been suggested. Interestingly, some studies reported a negative impact of too high serum P4 levels during HRT-FET. The pathology of endometriosis is dominated by an endometrial disruption of progesterone and oestrogen signalling pathways. This results in intra-endometrial oestrogen dominance, and leads to progesterone resistance which negatively impacts endometrial receptivity and function.

Until now no study explored the optimal serum P4 level in the endometriosis patient undergoing HRT-FET.

Study design, size, duration

A cohort study including 262 HRT-FET cycles in 179 patients, undergoing transfer of warmed blastocysts, deriving from freeze all cycles from January 2016 to august 2019.

Participants/materials, setting, methods

Patients were diagnosed with endometriosis either by laparoscopy or by ultrasound in cases with visible endometriomas. Pre-treatment consisted of 42 days of oral contraceptive pill and 5 days' wash-out, followed by 6 mg oral oestrogen daily. Intensive exogenous progesterone supplementation, including vaginal progesterone gel 90mg/12h commenced when the endometrium was ≥7mm. From the 4th day of progesterone patients also received intramuscular progesterone 50mg. Blastocyst transfer was scheduled for the 6th day of progesterone.

Main results and the role of chance

The mean P4 level was 103.1 ±44.4nmol/l and the overall positive HCG, live birth (LBR) and total pregnancy loss rates (TPLR) were 60%, 39% and 34%, respectively. The optimal serum P4 cut-off level was 118nmol/l defined as the maximum of the Youden index. No significant differences were seen between patients above or below 118nmol/l as regards age, BMI, fertilisation method or blastocyst score. In a total of 33% of cycles (86/262) the P4 level was ≥118nmol/l, and the unadjusted LBR was significantly higher in the high P4 group 51% (44/86) versus 34% (59/176) (p = 0.006) in the low P4 group. Furthermore, a non-significant difference in TPLR was found: 41% vs 25 % in favour of high P4 (p = 0.066).

A logistic regression analysis showed that patients with P4 levels ≥118nmol/l were more likely to achieve a live birth compared to patients with P4 levels &lt;118nmol/l; (odds ratio 2.1 [95% confidence interval 1.2 - 3.7] after adjusting for age, BMI, blastocyst score, blastocyst age (day 5 or day 6) and number of blastocysts transferred.

Limitations, reasons for caution

Cohort study with data prospectively registered and retrospectively analyzed. The estimated serum cut-off for P4 of 118nmol/l is valid for vaginal progesterone gel 90mg/12h and intramuscular progesterone 50mg from the 4th progesterone day; whether the cut-off is applicable for other progesterone regimens needs to be explored.

Wider implications of the findings

The optimal luteal P4 level of the endometriosis patient undergoing HRT-FET is significantly higher than that estimated for the "standard" patient due to endometrial progesterone resistance. Luteal phase P4 monitoring is mandatory to obtain the highest LBR in the endometriosis patient undergoing HRT-FET.

Trial registration number

1-10-72-4-17