The G Protein-Coupled Estrogen Receptor GPER in the Development and Progression of Cancer
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsTorres-López et al. propose a manuscript entitled "The G protein-coupled estrogen receptor GPER in the development and progression of cancer" for publication for Receptors. This article is well written and very interesting. However, I have some remarks and questions.
Abstract:
- Page 1, line 21: The authors claim the evidence of GPER isoforms. A paragraph should be devoted to GPER isoforms, which are not discussed.
Introduction:
- Page 1, line 39. What do you mean by "[...] in association with ERa [...]", exactly? Functionally associated with ERa? In interaction with ERa? Concomitantly expressed with ERa? Specify.
- Page 2, Line 45 "[...] GPER exerts the same effects as nuclear ER [...]". This affirmation is confusing, the mechanism of GPER (at the membrane) and of nuclear ERs (in the nucleus) being very different. As highlighted in the manuscript, the exact role of GPER depends of the type of tissue, the cell line and the experimental conditions.
Text:
- At the beginning of this paragraph, the authors should specify that "GPER is a class A (rhodopsin-like) GPCR".
- Page 3, Line 86. "[...] with a volume of 457 Å3" It would be interesting to compare the volume of the ligand-binding pocket of GPER with the one of ERa.
- Page 3, Figure 1. Peptidic GPER modulators are strongly lacking in the figure 1. Update the table.
- Depending on the experimental conditions, G-1 is agonist or antagonist, in the context of breast cancer. In the case of inverse agonists, is the response more stable or not?
- Page 3, Lines 102, 103. "[...] ligand molecules that effectively bind to GPER must possess chemical properties, such as the presence of aliphatic chains and hydrophobic residues [...]" What do you mean by "hydrophobic residues"? This terminology is used for peptides and proteins.
- In the part 2.2.1. (Canonical GPER agonists), a figure showing the distribution of the key residues in the GPER ligand-binding site is mandatory. In the present form, it is difficult to understand this part of the manuscript without a figure. Same remark for the second (fulvestrant), the sixth (Estriol) and the eighth (oleuropein) paragraphs, page 9.
- Page 4, line 123. What do you mean by "Canonical GPER ligands"? (title of the paragraph).
- Page 4 and 5. Explain by which approach the thermodynamic parameters and the values Kd, Ki, IC50 and EC50 have been determined.
- Page 5, line 170: Molecular docking. Explain briefly how GPER structure models have been obtained for docking calculations. Idem Page 9, line 234.
- Page 10, line 303. Is cadmium the only divalent cation supporting estrogenic activity through GPER?
- Page 11, §2.3 "GPER signaling pathways in cancer cells". It has been demonstrated that GPER was able to interact physically with ERa66 and ERa36. Considering the fact that GPER and ERa66 bind E2, this point should be discussed. What means these interactions in terms of biological response? Is finally GPER a coactivator of ERa66 or an estrogen receptor. What is the role of ER36, in this context?
- Page 13 - Role of GPER in human cancer - In silico studies in different cancer types. Explain in few words how such in silico investigations have been performed.
- Specify the roles of GPER at the membrane, in the Golgi apparatus and in the nucleus.
Comments on the Quality of English LanguageNo comment
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis review by L. Torres-Lopez and colleagues describes the role of the G protein-coupled estrogen receptor (GPER) in the development and progression of cancer. This review provides a detailed oversight of many studies that investigate the role of GPER and its ligands in cancer.
I have several suggestions that might improve the quality of the manuscript.
- 2.2. GPER ligands: both "canonical" and "non-canonical" ligands are described. But it is not clear what is meant with "canonical" and "non-canonical". This should be explained in the text.
- for some of the described agonists/antagonists quantitative data are provided, like Kd and EC50 values (line 124) or IC50 values (line 165). But it is not mentioned which assays were used to determine these values. Is it solely from binding studies (and if yes, what type of binding assay?), or also from functional GPCR assays? This type of information would be of interest to the reader.
- paragraph 2.2.1. Canonical GPER agonist. The title of this paragraph is somewhat misleading since the paragraph contains information about agonists (eg. G1, E2), but also about antagonists (G15, G36). The information about the agonists and antagonists seems also a bit mixed up. I believe it would be more clear to talk about the agonists first, and then continue with the antagonists.
- line 351-352: the description of the role of heterotrimeric G protein signalling is very limited. I wonder to what extent G protein signaling has been studied for GPER. In particular since GPER is able to bind structurally diverse ligands, I wonder if different agonists would activate different G proteins or not? This simply may have not been studied yet, but maybe you can elaborate a bit more on this topic.
- Figure 4 is difficult to understand. In particular, the "localization" column should be better explained (do you want to distinguish between nuclear, cytosolic and cell membrane expression?), and also the color codes for "primary tumor expression" are unclear for me. I would suggest to rethink and adapt this figure.
Minor remarks:
- line 70: the MW of GPER is 42 kDa, but can be increased to 59, 80 and 124kDa due to glycosylation. 124 kDa seems rather high to be solely explained by glycosylation, maybe this was explained by receptor dimerization?
- line 90-94: seems that two sentences were mixed. Rephrase.
- line 179: In binding mode I,....forms hydrogen bonds..."E2" is missing.
- line 226: [39]. As well as....Sentence should be adapted.
- line 421: (GBM) patients, despite gender [29]. "Despite gender" should be removed?
- line 473: ... or who did not received it. Should be did not receive it.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have provided substantial modifications to improve their manuscript. However, I have two last remarks:
1. The authors will find information on GPER residues interacting with ERα17p in Kampa et al. Cells, 2023, 12, 653.
2. ER-α36 and ER-α66 should be written as followed: ERα-36 (or ERα36) and ERα-66 (or ERα66), respectively
Comments on the Quality of English LanguageMinor editing of English language required
Author Response
Thanks for the comments. The information concerning the suggested article was added, as well as its reference (Changes are highlighted in yellow). Currently there is no consensus on the correct way to write ER-α66 or ER-α36, even both ways are found in works previously published by various authors. For this reason, it was not modified in the text.
English writing was improved.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have improved the clarity and quality of the manuscript. All issues/remarks were addressed.
Only the sentence line 99-100 still seems a bit mixed up. Please check.
Author Response
Thanks for the comments, the sentence was restructured to avoid confusion. Changes are highlighted in yellow.
